bluuebunny/crossref_metadata_2025 huggingface dataset:
System Level Performance and Emissions Evaluation of Renewable Fuels for Jet Engines
Authors: Lokesh Kadambari , Sethi Vishal , Nikolaidis Theoklis , Karumbaiah Devaiah
Published: February 2015

Incessant demand for fossil derived energy and the resulting environmental impact has urged the renewable energy sector to conceive one of the most anticipated sustainable, alternative “drop-in” fuels for jet engines, called as, Bio-Synthetic Paraffinic Kerosene (Bio-SPKs). Second (Camelina SPK & Jatropha SPK and third generation (Microalgae SPK) advanced biofuels have been chosen to analyse their influence on the behaviour of a jet engine through numerical modelling and simulation procedures. The thermodynamic influence of each of the biofuels on the gas turbine performance extended to aircraft performance over a user-defined trajectory (with chosen engine/airframe configuration) have been reported in this paper. Initially, the behaviour of twin-shaft turbofan engine operated with 100% Bio-SPKs at varying operating conditions. This evaluation is conducted from the underpinning phase of adopting the chemical composition of Bio-SPKs towards an elaborate and careful prediction of fluid thermodynamics properties (FTPs). The engine performance was primarily estimated in terms of fuel consumption which steers the fiscal and environmental scenarios in civil aviation. Alternative fuel combustion was virtually simulated through stirred-reactor approach using a validated combustor model. The system-level emissions (CO2 and NOx) have been numerically quantified and reported as follows: the modelled aircraft operating with Bio-SPKs exhibited fuel economy (mission fuel burn) by an avg. of 2.4% relative to that of baseline (Jet Kerosene). LTO-NOx for the user-defined trajectory decreased by 7–7.8% and by 15–18% considering the entire mission. Additionally, this study reasonably qualitatively explores the benefits and issues associated with Bio-SPKs.
Understanding the Steady and Transient Behavior of the Moderately Loaded High Speed Axial Flow Compressor Stage at Off-Design Conditions
Authors: Alone Dilipkumar B. , Kumar Subramani Satish , Thimmaiah Shobhavathy M. , Mudipalli Janaki Rami Reddy , Pradeep A. M. , Ramamurthy Srinivasan , Iyengar Venkat S.
Published: February 2015

High performance high speed transonic axial flow compressors and fans are the major components of efficient aero-engines. Engine operating envelope and performance normally depends on the compressor performance and its distortion tolerance. Even though the high speed compressors are favorite amongst modern aero-engines, they are more prone to instabilities like surge and stall, which further restricts the engine operations. The present paper deal with experimental study carried on a moderately loaded high speed single stage axial compressor and is focused on the steady state as well as transient behavior at off-design conditions. The single stage transonic compressor is designed for stage total pressure ratio of 1.35 and delivers 23 kg/s mass flow rate at corrected speed of 12930 rpm. The stall inception phenomenon is studied using high frequency miniature Kulite pressure transducers and hot wire probe. The fluctuations in the wall static pressure were also studied by placing three Kulite transducers, one at rotor inlet, second at rotor exit and the third at stator exit. The unsteady pressure signals from these Kulite transducers are processed and analysed to understand the stall inception process. The FFT was performed to identify the stall frequency and pressure oscillation amplitude. Unsteady pressure signals clearly shows the instabilities occurred at the rotor inlet and then gradually moves towards the rotor exit, while the flow at the stator exit remains undisturbed. The intensity of the instabilities along the blade span was also studied using three point Kulite rakes placed at the rotor inlet. Stable operating margin of the compressor was evaluated by deriving the compressor stage performance map. The compressor stage performance map was derived using conventional instrumentation like total pressure rakes and thermocouples. The compressor stage experienced abrupt stall at higher operating speeds. The turbulence intensity was evaluated using single component hot wire probe. Maximum stable operating range of 22% is obtained at 50% design speed. The flow parameters were also evaluated at the rotor inlet and rotor exit using aerodynamic probe at full flow and near stall conditions.
Numerically Understanding the Steady State Response of Single Stage Transonic Axial Flow Compressor to Axial Locations of Step for Stepped Tip Clearance
Authors: Vashi Hardik K. , Alone Dilipkumar Bhanudasji , Choksi Harish S.
Published: February 2015

This paper describes the steady state numerical work carried out to study the influence of providing stepped tip clearances at various axial locations along the rotor chord on the performance of the single stage transonic axial compressor. Uniform tip clearance study on compressor under consideration showed performance deterioration of compressor at higher tip clearance of 2mm [3.4% of rotor axial chord] therefore in order to improve performance of compressor, stepped tip clearance method was introduced. Commercially available Ansys Fluent 12.0 software was used to perform steady state RANS simulations with three dimensional implicit pressure based solver and SST K-ω as turbulence model. Stepped tip clearance concept is based on providing smaller tip clearance in front portion and providing higher tip clearance after step above the rotor. In present case, study was carried out for stepped tip clearance with steps at four different axial locations [i.e. 10, 20, 40 & 60 % of rotor chord from leading edge of rotor] and results were compared with baseline model of 0.5 mm [0.9% of rotor axial chord] uniform tip clearance at 100% speed. The stepped tip clearance combinations used for the analysis was 0.5–2mm. It was observed that there was increase in compressor peak efficiency & peak pressure ratio for all stepped clearance cases. A trend was noticed where there was relative increase in peak efficiency as well as peak pressure ratio when step was moved downstream along rotor chord [i.e. moving from 10% to 60% axial location]for one of the combinations stepped tip clearance. Stall margin improvement was observed for all cases of stepped tip clearance. Stall margin gain obtained was higher when step was provided in front portion above rotor [i.e. 10 & 20 % axial location] compared to stall margin improvement when step was provided in rear portion above rotor [i.e. 40 & 60% axial location]. It can be concluded that stepped tip clearance provided near leading edge shows potential in improving performance for compressor under consideration. Numerical analysis of single stage has been carried out but data has been presented for rotor only to study the flow changes occurring in rotor vicinity created by implementation of stepped tip clearance method.
Numerical Investigation of Crosswind Effect on Different Rear Mounted Engine Installations
Authors: Xie Hairun , Wu Yadong , Wang Anjenq , Ouyang Hua
Published: February 2015

The rear-mounted engine is widely used in business and regional jets. It is a “clean wing” design. The engine is mounted behind the wing, so that the inlet/outlet of the nacelle has a minor influence on the flow over the wing. The engine thrust line is close to the fuselage axis. As a result, the asymmetric yaw moment will be smaller when single engine stall occurs.

Strict regulations and requirements were set by certification agencies to assess aircraft maneuver capability as well as engine operating characteristics. These regulations are mainly defined to evaluate structural strength, aerodynamics, & engine/aircraft performance. However, due to the nature of the complexity of the flow field at the air intake, the inlet compatibility of fuselage mounted engines becomes one of the most complicated & challenging items to meet FAR33 as well as FAR25 certification requirements, especially during cross wind operating conditions.

This research paper discusses the inlet compatibility of rear-mounted aircraft engines with respect to the installed configuration and crosswind operating conditions. Models of two installed configurations, set by the relative position of engine to the fuselage and the wing were created. In each case, the engine inlet flow field was calculated at various ambient wind conditions. Comparisons of the total pressure profile at the air intake were made to assess the likelihood of flow separation at the inlet of engine. Inlet distortion levels of corresponding total pressure profiles were calculated for each operating and installed condition. Assessments are made based on intensive usage of CFD analysis of different engine installations and operating conditions. The flow field information obtained by CFD calculation reveals a close coupling phenomenon exists among engine installations, cross wind, and inlet capability.
Experiments on Leading-Edge Induced Separated Shear Layer Under Various Imposed Pressure Gradients
Authors: Anand K. , Sarkar S. , Thilakan N.
Published: February 2015

The behaviour of a separated shear layer past a semi-circular leading edge flat plate, its transition and reattachment downstream to separation are investigated for different imposed pressure gradients. The experiments are carried out in a blowing tunnel for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The mean flow characteristics and the instantaneous vector field are documented using a two-component LDA and a planar PIV, whereas, surface pressures are measured with Electronically scanned pressure (ESP). The onset of separation occurs near the blend point for all values of β (flap angle deflection), however, a considerable shift is noticed in the point of reattachment. The dimensions of the separation bubble is highly susceptible to β and plays an important role in the activity of the outer shear layer. Instantaneous results from PIV show a significant unsteadiness in the shear layer at about 30% of the bubble length, which is further amplified in the second half of the bubble leading to three-dimensional motions. The reverse flow velocity is higher for a favourable pressure gradient (β = +30°) and is found to be 21% of the free stream velocity. The Reynolds number calculated based on ll (laminar shear layer length), falls in the range of 0.9×104 to 1.4×104. The numerical values concerning the criterion for separation and reattachment agree well with the available literature.
Effect of Guide Vane Angle on Wells Turbine Performance
Authors: Halder Paresh , Samad Abdus
Published: February 2015

Wells turbines are used in oscillating water column wave energy system and the turbine has a stagger angle of 90°. Numerical analysis is performed to analyze the performance of the turbine in the present work. A commercial code ANSYS-CFX® v14.0 was used for the simulations at different flow coefficient, different angles and a constant rotational speed. The turbulence model was k-ω SST. Higher guide vane angle produced higher efficiency of the turbine and the efficiency (enhanced) change was contributed because of the vortex formation in different locations in the flow passage or near the blade surface.
Experimental Investigation of Squeeze Film Damper Characteristics at High Speed Rotor Configurations
Authors: Kandasamy Jayaraman , Jaiswal B. L. , Sarasu P. , Sivaperumal S. , Babu Dilli , Kumar Ashok
Published: February 2015

High performance turbo machinery demands high shaft speeds, increased rotor flexibility, tighter clearances in flow passages, advanced materials, and increased tolerance to imbalances. Operation at high speeds induces severe dynamic loading with large amplitude journal motions at the bearing supports. Squeeze film dampers are essential components of high-speed turbo machinery since they offer the unique advantages of dissipation of vibration energy and isolation of structural components, as well as the capability to improve the dynamic stability characteristics of inherently unstable rotor-bearing systems. A bearing test rig is developed using 350 KW motor with variable frequency drive and has the potential of maximum operating speed up to 20,000 rpm. A squeeze film damper is used between the bearings and housing to reduce the unbalance forces transmitted to the pedestal by introducing an additional damping and thereby reduces the amplitude of vibration to acceptable level. The test rig instrumentation is capable of detecting bearing critical speed of the test rotor, and has been used for parametric studies and to monitor the temperature profile, vibration levels and pressure distribution of SFD oil film. The first critical speed of the test rotor is measured. The vibration level of the rotor system is increased with the rise of axial load together with speed. It is estimated that under all the conditions presence of oil in SFD zone reduces the vibration levels.
Energy and Exergy Analysis of the Kalina Cycle Based Combined Cycle Using Solar Heating
Authors: Maheshwari Mayank , Singh Onkar
Published: February 2015

Gas and steam combined cycle has Brayton cycle and Rankine cycle as topping and bottoming cycles respectively. Gas based topping cycle has flue gases leaving at high temperature which are utilized in heat recovery steam generator for steam generation. The steam thus generated is used for running steam turbine in bottoming cycle. It is seen that the heat recovery steam generator although offers reasonable heat recovery from flue gases but the temperature variation profile of gas does not match with that of steam generation. The use of ammonia in place of steam as working fluid offers a good matching of temperature profile of flue gas and ammonia and thus has capability to offer effective utilization of waste heat. In present work thermodynamic analysis of Kalina cycle used in combined cycle has been carried out. It includes the performance evaluation in terms of ammonia mass concentration, turbine inlet temperature and cycle pressure ratio. The results show that on increasing the ammonia mass fraction the efficiency of the cycle decreases up to ammonia mass concentration of 0.7 but beyond that efficiency starts increasing. It also indicates that by installing the solar heating, there occurs a heat gain up to 5% as compared to without solar heating for any given operating parameters.
Techniques and Methods to Improve the Dynamic Strength of Gas Turbine Engines Compressor Rotor Wheels
Authors: Kolmakova Daria , Popov Grigorii , Shklovets Aleksandr , Ermakov Aleksandr
Published: February 2015

The approaches to reducing the alternating stresses in the compressor blades, arising at a resonance, are discussed in paper. Maximum alternating stresses in blades of the fifth stage of intermediate pressure compressor (IPC, that operating under the gas flow circumferential variation conditions, are defined on the basis of the forced blade oscillations calculation method. Parametric CFD-model which allows to introduce different stagger angles and circumferentially alternating blade pitch at the guide vanes of IPC fifth stage was created to reduce the stresses. The flow circumferential variation was reduced by changing these parameters and as a consequence the resonant stresses were decreased by more than 2.5 times.
Numerical Simulation of Inclined Injection of Polydisperse Polykinetic Spray in a Crossflow Using Quadrature Method of Moments
Authors: Mondal Sudeepta , Mukhopadhyay Achintya
Published: February 2015

Liquid fuel is introduced as spray into a gaseous crossflow in many combustion applications like afterburners in gas turbines, ramjet and scramjet combustors. The transport phenomenon of a polydisperse polykinetic spray injected with an inclination in a crossflow has been analysed using Quadrature Method of Moments. Providing an inclination angle to the spray has been accompanied with a more or less uniform distribution of particles, unlike a distinct segregation of larger and smaller diameter particles as observed in the case of vertical injection. The upstream inclined injection in the crossflow yielded a region of stagnation of particles, irrespective of their sizes. This region corresponds to the location where the spray particles equilibrate with the crossflow, whereby they lose their momentum and are swept away by the carrier phase. The downstream injection, on the other hand, showed distinct horizontal and vertical size-based segregation along with regions of accumulation of particles.
Numerical Analysis to Investigate the Effect of Swept Rotor on the Overall Performance of a Transonic Compressor Stage
Authors: Thimmaiah Shobhavathy M. , Gurikelu Ramesha , Sherief Nisha
Published: February 2015

This paper presents the steady state numerical analyses carried out to investigate the effect of forward and backward swept rotor on the overall performance and stability margin of single stage transonic axial flow compressor. Initially, the analyses were carried out on a radially stacked rotor/baseline configuration and obtained the overall performance map of the compressor stage. These results were compared with the available experimental data for validation. Further, investigations were carried out on geometrically modified rotor with six configurations having 5, 10 and 15° forward and backward sweep. A commercial 3-Dimensional CFD package, ANSYS FLUENT was used to compute the complex flow field of transonic compressor rotors. The flow field structures were studied with the help of Mach number total pressure contours. The results of modified rotor geometry indicated that the peak adiabatic efficiency and the total pressure ratio for all the tested forward and backward swept rotor configurations are marginally higher than that of the baseline configuration at all speeds. The operating ranges of all the swept rotor configurations are found to be higher than that of the baseline configuration. The operating range is broader at lower operating speeds than at design speed condition. Rotor with 10° forward sweep and 5° backward sweep indicated the noteworthy improvement in the operating range against the baseline configuration. The stability margin of 11.3, 6.6, 5.2 and 3.5% at 60, 80, 90 and 100% of the design speed respectively compared to the baseline configuration obtained from 10° forward sweep. Rotor with 5° backward sweep showed the stability margin of 12, 4, 3.9 and 3% at 60, 80, 90 and 100% of the design speed respectively compared to the baseline configuration.
Study of Simulated Distortion Waves in an Axial Flow Fan
Authors: Kumar Prashant , Roy Bhaskar
Published: February 2015

Inflow distortion is a problem encountered during axial fan/compressor operation. There are a large number of experimental studies that have been carried out to study the distortion effects on the axial fan/compressor performance by using wire mesh screens, by blocking inlet passage and physically disturbing the inlet flow. When the compressor experiences off design operation, it is likely to experience an inlet distortion, which determines its operational sustainability. Every compressor in each flight segment undergoes non-uniform inlet flow fields and responds differently to that of a clean inlet flow, for which it is designed. To meet specific performance requirements, it is often required for a compressor to pass through off-design environments. Distortion, simulated as waves or combination of waves in propagation, have been studied in this work. It has been observed that the effect of distortion depends on types of waves applied, area covered by distortion, operating speed of the fan/compressor & location of the distortion waves with respect to blade profile. For a given velocity in distorted passages spike wave has more detrimental effect compare to normal distortion wave or a triangular wave. A few combination distortion waves have been studied too.
Intelligent Biogas Fuelled Distributed Energy Conversion Technologies: Overview of a Pilot Study in Norway
Authors: Assadi Mohsen , Majoumerd Mohammad Mansouri , Jana Kuntal , De Sudipta
Published: February 2015

It is foreseen that distributed power generation, using biogas and natural gas as fuel, will play increasingly important role in the future European energy market. These technologies are presenting controllable power generation capacity as complementary to the installed intermittent renewable power generation in terms of wind and solar.

A nationally funded project was initiated in Stavanger, Norway in 2010, led by the Center for Sustainable Energy Solutions (cenSE), to investigate use of existing small scale energy conversion technologies developed for natural gas, using as much as possible biogas mixed with natural gas without any hardware modifications to the energy conversion units. Three test setups with a micro gas turbine (100 kWe), a gas engine (11 kWe) and a short stack of solid oxide fuel cell consisting of six cells (30–40 We) were installed for experimental studies, providing necessary data for model validation and development of data driven models for engine performance monitoring.

This paper reports the results of the project, concerning mapping the operational window for use of mixture of simulated biogas (50% methane, 50% CO2) and natural gas for each technology as an enabler of biogas utilization with natural gas as fallback solution. The CO2 reduction potential, when natural gas is replaced with biogas, is also presented. Moreover, the capability of using data driven models based on artificial neural network for online monitoring and control of the engine performance at various operational conditions is shown.

Detailed reporting on various aspects of fuel composition and technology impact has been conducted earlier. This paper provides a total overview and a comparison of performance of the technologies tested in this study.
Validation of LCF Life of Turbine Rotor Assembly of a Turbo-Shaft Engine Through Cyclic Spin Test
Authors: Roy Hardik , Muthu S. Esakki , Udayanan P. , Degaonkar Girish K. , Anbarasan Selwyn
Published: February 2015

Gas turbine rotors are high speed rotating components which operate under high temperatures. These turbine rotors undergo repeated cycles of low speeds to high speeds and therefore low stresses to high stresses which lead to low cycle fatigue failure. This low cycle fatigue leads to initiation of cracks at high stress areas like bolt holes, blade slots or disc bore. During design the life obtained through numerical methods is verified by cyclic spin tests. This particular paper talks about the spin testing of turbine rotor assembly of a turbo-shaft engine to validate its low cycle fatigue life obtained through analysis. These three stage turbine rotors were indigenised for cost savings. The life of the indigenously designed rotors were required to be the same as the turbine rotors being supplied by the engine OEM’s. Since the test rig which was used to validate the life of the rotors had a limitation of applying uniform temperatures, there was a need to develop a test schedule that simulates the operating conditions of the actual engine rotors.

The work was carried out in two phases. In the first phase FEA tools were utilised to find out stress and strain levels of the turbine rotors by applying actual engine load conditions. Since rotor assembly was tested under uniform temperature in the test rig a combination of centrifugal load and temperature that would result in the same factor of safety levels of the rotors as in the actual engine conditions was arrived at in an iterative manner. Once the right combination was achieved the life of the engine rotors under test conditions was estimated numerically. In the second phase cyclic spin test was carried out on the turbine rotor assembly at equivalent load conditions. At regular intervals dimensional and NDT checks were carried out on the rotor assembly to find out crack initiation. The life of the rotor assembly which was estimated with the help of FE tool was validated through spin test.
Effect of Flow Pulsations in Premixed, Swirl Stabilized Combustor
Authors: Sharma Aayush K. , Sen Uddalok , Mahapatra Pallab Sinha , Sen Swarnendu , Mukhopadhyay Achintya
Published: February 2015

In the present work, a numerical model has been developed using ANSYS Fluent 14.5 to simulate the combustion phenomenon in a partially premixed, swirl-stabilized, LPG-fueled gas turbine combustor. In a practical gas turbine combustor, pulsations in the flow at the air side cannot be avoided which can lead to thermoacoustic instabilities. The primary objective of the study is to numerically analyze the effect of such pulsations on the fluid flow and combustion process inside the combustor. Different parameters like static temperature, progress variable and product formation rate are compared at the outlet plane of the combustor. The effect of change in the parameters like amplitude and frequency of the sinusoidal air flow input has also been investigated in the present study. It is observed that the solution changes from periodic to quasi-periodic at a higher amplitude condition. The numerical model was qualitatively validated against experiments performed on a laboratory-scale premixed, swirl-stabilized, gas turbine combustor.
Prediction and Comparison of Critical Speeds and Potential Excitation Using In-House Developed Software for an Integrally Geared Centrifugal Air Compressor
Authors: James Mathew P. , Reddy Pandillapalli Pavan Kumar , Gopalakrishnan Swaminathan
Published: February 2015

Integrally Geared Centrifugal Air Compressors (IGCAC) are becoming popular in many industrial applications. Development of such compressors requires in depth Rotordynamic Design and Analysis. To facilitate this, an in-house computer program based on transfer matrix method was developed using MATLAB® software. This computer program is capable of computing rotordynamic parameters such as static deflection, critical speed and interference diagram, and can output critical speed map, mode shape, unbalance response, orbit, for lateral direction.

This software was used to analyze a two stage IGCAC with two impellers on a simply supported rotor running above second critical speed, driven by a two pole induction motor through a step-up gearbox. Undamped critical speed map, an output from the program was used to predict intended bearing stiffness for design. Using the above data and commercially available software DyRoBeS© a suitable bearing was designed. The speed dependent bearing characteristics, an output from DyRoBeS©, were used to determine damped unbalance response plot for a given residual unbalance. Corresponding to a maximum peak in unbalance response the damped critical speed and amplification factors (AF) were found out. The results from the newly developed software were compared with prediction from DyRoBeS©. It was found that critical speed was within 5% and AF was of the same order. Results from in-house software were comparable to that from DyRoBeS©. Based on the guidelines from API 684, the AF and separation margins were determined.

A prototype IGCAC compressor as described above was built and tested. The testing included the collection of steady state, coast-up and coast-down data. Using the coast-up, coast-down data, a Bode plot was created. From this the critical speeds and AF’s were determined and compared with results from in-house software. It was found there was an error of less than 5% for the critical speed and around 5% for AF from the predicted results. For the same compressor a study on the potential excitation frequencies due to unbalance, impeller-diffuser and impeller-scroll tongue interactions were calculated. FFT of the steady state vibration data was deduced. It was found that the calculated frequency and measured frequency at maximum amplitude were aligning. Further noise measurements were recorded based on sound intensity as per guidelines in ISO 9614. The impeller-tongue interaction frequencies for stages were seen in the processed noise data. It was found that the predictions were in good agreement with the test results.
Three-Dimensional Finite Element Analysis of Bolted Joint With Helical Thread Connection
Authors: Bommisetty Kondaiah , Narayanan Kumar
Published: February 2015

Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfactory results. In this paper, an effective mesh generation scheme is used which can provide accurate helical thread model to analyse specific characteristics of stress concentrations and contact pressure distributions caused by the helical thread geometry. Sector model of bolted flange joint has been analysed for pretension alone and combination of pretension and axial load. Using the finite element (FE) model with accurate thread geometry with pretension, the thread root stresses, contact pressure along the helix and at the nut loaded surface in the circumferential direction have been studied. The peak stress occurs at the first engaged bolt thread root from nut loaded surface. This stress at the thread root gradually decreases towards the free face of the nut. The contact pressure at nut bearing surface varies in the circumferential direction because of the circumferential variation of the stiffness of engaged threads adjacent to the nut loaded surface. The axial load along the engaged threads gradually decreases from nut loaded surface to zero towards the free surface of the nut.

Results from analysis with pretension and axial load indicate that the contact separation starts at the inner radius of flange and grows towards outer diameter of flange as the axial load is increased in the bolted flange joint. It is observed from the analyses that the load is shared by flanges when the external applied axial load is up to 15% of preload, and beyond this, bolt starts sharing external load. The maximum stress occurs at the first engaged bolt thread root. Most of the bolt failures are at the first engaged thread. The study suggests that it is necessary to consider threads in FE model to obtain accurate contact pressure, thread stress, stiffness and bolt load predictions. These critical observations provide insight for optimization of bolted flange joint to meet the structural requirements and weight optimisation.
A CCGT Based Polygeneration Using Rice Straw: Simulation by Aspen Plus®
Authors: Jana Kuntal , De Sudipta , Assadi Mohsen , Majoumerd Mohammad Mansouri
Published: February 2015

Demand of secondary energy is ever increasing. Presently, fossil fuels supply majority of it. Energy technologists are currently facing the formidable challenge of meeting this demand with minimum environmental impact, specifically reduced CO2 emission to minimize ‘climate change’. Also new technology development for efficient energy conversion is needed for renewable resource (e.g. biomass) utilization. Rice straw is an agricultural residue and has good calorific value to be used as an energy resource. For the efficient utilization of rice straw, combined cycle gas turbine (CCGT) based polygeneration is a possible option to deliver multiple utilities. In this paper, a polygeneration plant is proposed to deliver power, cooling, heating and desalinated water. It was simulated by Aspen Plus®. Results show that polygeneration has good potential in power generation as well as for various other utilities. Effects of gasification parameters and gas turbine compression ratio are also studied. Results show that optimum equivalence ratio is 3.5–4 for maximum fuel energy savings ratio and for maximum exergy efficiency. Higher GT-cycle compression ratio results more power output but other utility outputs decrease with increase in compression ratio.
Experimental Investigation of a Hybrid Atomizer’s Spray Characteristics in Variable Flow Condition by Using Alcohol Blended Diesel Fuel
Authors: Garai Amlan , Mondal Sudeepta , Sen Swarnendu , Mukhopadhyay Achintya
Published: February 2015

Heavy duty marine gas turbine combustors use diesel as fuel. One of the promising alternative fuels for gas turbine applications is ethanol, both in pure and blended form. The present work investigates spray characteristics of ethanol-blended diesel. A hybrid atomizer is selected for this experimental study where the fuel stream is sandwiched between two annular air streams. The air and fuel streams come into the atomizer tangentially and produce a high degree of swirl. Air inlets of the atomizer are varied in co and counter swirl directions with respect to the fuel inlet direction. Also the flow rates of the inner and outer air streams are varied during the process. With increase in flow rates of the air streams the turbulence increases. Spray ligament formation, ligament breakup and drop formation from the ligament are clearly visible during the experimental investigation. Breakup length, spray cone angle and spray pattern are major areas for analysis for understanding the nature of spray formation by an atomizer. Two back lights and a high speed camera are used for capturing the images of the spray. These images are used for analyzing the characteristics of the spray. The inner and outer air flow rates effectively influence the spray character of this atomizer. The air and fuel flow rates and swirl orientation play an important role for understanding the effect of the spray character by the air flow.
Investigation of Combustion Instability in a Swirl-Stabilized Combustor Using Symbolic Time Series Analysis
Authors: Ramanan Vikram , Chakravarthy S. R. , Sarkar Soumalya , Ray Ashok
Published: February 2015

A laboratory-scale swirl-stabilized combustor is experimentally characterized for various configurations involving variable air flow rates and different fuel injection locations. Unsteady pressure and heat release rate measurements were obtained simultaneously in order to determine the stability map of the combustor for the experimented configurations. It is observed that a sharp rise in pressure amplitude coincides with a break in the dominant spectral content variation with the inlet Reynolds number. The time series data were analyzed by using the tools of symbolic dynamic filtering and the divergences among the outputs of each sub-class of observations were obtained as anomaly measures. In the proposed method, symbol strings are generated by partitioning the (finite-length) time series to construct a special class of probabilistic finite state automata (PFSA) that have a deterministic algebraic structure. The anomaly measures are defined based on the probabilistic state vectors distribution across each sub class. The method which is based on representing a given time series data as a set of PFSA is observed to be capable of predicting an impending combustion instability as well as to distinguish between the symbol-state distribution among various instability conditions. The measure also successfully captures changes in the thermoacoustic regime as a function of the fuel injection location.
Design Optimization of Wind Turbine Using Fluid Structural Interaction Analysis and Genetic Algorithm
Authors: Karthikeyan Ganesh Ram Ramanujam , Mehta Akshan Paresh , Ramanujam Karthikeyan , Venkatesan Kalaichelvi
Published: February 2015

Aerodynamics of wind turbine blade is an important field of research. In the present study, a multi stage optimization process has been evaluated on a baseline wind turbine blade. Genetic Algorithms (GAs) are applied as a generative and search procedure to look for optimized design solutions in terms of aerodynamic performance of the airfoil selected for the study. The MatLab Genetic Algorithm toolbox interfaced with Xfoil, an interactive program for the design and analysis of airfoils, was implemented for the profile design optimisation. To analyse the performance of the optimized profile, the ANSYS Fluent toolbox was used to conduct the 3D computational fluid dynamics analysis of a section of the wind turbine blade before and after optimization. The total deformation and Von-Mises stress of the wind turbine blade caused due to Fluid-Structure Interaction is analysed using the ANSYS simulation software.
Characterization of Mixing and Flow Properties From Numerical Simulation of Cold Flow in Non-Premixed Combustor
Authors: Mondal Sirshendu , Mukhopadhyay Achintya , Sen Swarnendu , Polifke Wolfgang
Published: February 2015

In this work, large eddy simulation is applied to simulate cold flow in a combustor of non-premixed type. Air is introduced axially from the bottom of a cylindrical combustor whereas fuel is introduced directly in the combustion chamber. Two different geometries of fuel injection are taken which have been experimentally studied at Jadavpur University, India. Fuel is injected using two alternative orientations of the holes. In one orientation (referred to in this article as the vertical configuration), the fuel comes in vertically in parallel and counter-flow with the air stream. In the other orientation (referred to as the horizontal configuration), the fuel is injected horizontally at cross flow with the air stream. Two different kinds of dynamics have been achieved with two orientations in the experimental study [1]. In the present study, effort has been given to explore the flow behavior and mixing characteristics by simulating the combustion chamber with fuel injection similar to the experimental one. It is found that mixture fraction is more homogeneous due to the vortices formed downstream of the fuel inlet section for the horizontal configuration and also its value mostly remains in the flammability limit. As the parallel flow of fuel jet in the wake region hampers the vortex formation, convective mixing is very poor with vertical fuel injection.
Turbulence-Transport-Chemistry Interaction in Statistically Planar Premixed Flames and Ignition Kernels in Near Isotropic Turbulence
Authors: Uranakar Harshavardhana A. , Chaudhuri Swetaprovo , Lakshmisha K. N.
Published: February 2015

Turbulence-transport-chemistry interaction plays a crucial role on the flame surface geometry, local and global reaction-rates, and therefore, on the propagation and extinction characteristics of intensely turbulent, premixed flames encountered in LPP gas-turbine combustors. The aim of the present work is to understand these interaction effects on the flame surface annihilation and extinction of lean premixed flames, interacting with near isotropic turbulence. As an example case, lean premixed H2-air mixture is considered so as to enable inclusion of detailed chemistry effects in Direct Numerical Simulations (DNS). The work is carried out in two phases namely, statistically planar flames and ignition kernel, both interacting with near isotropic turbulence, using the recently proposed Flame Particle Tracking (FPT) technique. Flame particles are surface points residing and commoving with an iso-scalar surface within a premixed flame. Tracking flame particles allows us to study the evolution of propagating surface locations uniquely identified with time. In this work, using DNS and FPT we study the flame speed, reaction rate and transport histories of such flame particles residing on iso-scalar surfaces.

An analytical expression for the local displacement flame speed (Sd) is derived, and the contribution of transport and chemistry on the displacement flame speed is identified. An examination of the results of the planar case leads to a conclusion that the cause of variation in Sd may be attributed to the effects of turbulent transport and heat release rate. In the second phase of this work, the sustenance of an ignition kernel is examined in light of the S-curve. A newly proposed Damköhler number accounting for local turbulent transport and reaction rates is found to explain either the sustenance or otherwise propagation of flame kernels in near isotropic turbulence.
Assessment of CFD Approaches for Next-Generation Combustor Design
Authors: Ajmani Kumud , Mongia Hukam C. , Lee Phil
Published: February 2015

An effort was undertaken to perform CFD analysis of fluid flow in Lean-Direct Injection (LDI) combustors with axial swirl-venturi elements for next-generation LDI-2 design. The National Combustion Code (NCC) developed at NASA Glenn Research Center was used to perform reacting flow computations on an LDI-2 combustor configuration with thirteen injector elements arranged in four fuel stages. Reacting computations were performed with a consistent approach for mesh-optimization, liquid spray modeling and kinetics modeling. Computational predictions of Emissions Index (EINOx) and combustor exit temperature were compared with two sets of experimental data at medium and high-power operating conditions, for two different pressure-drop conditions in the combustor. The NCC simulations predicted the combustor exit temperature to within 1–2% of experimental data. The accuracy of the EINOx predictions from the NCC simulations was within 10% to 30% of experimental data.
Full membrane spanning self-assembled monolayers as model systems for UHV-based studies of cell-penetrating peptides
Authors: Franz Johannes , Graham Daniel J. , Schmüser Lars , Baio Joe E. , Lelle Marco , Peneva Kalina , Müllen Klaus , Castner David G. , Bonn Mischa , Weidner Tobias
Published: February 2015

Biophysical studies of the interaction of peptides with model membranes provide a simple yet effective approach to understand the transport of peptides and peptide based drug carriers across the cell membrane. Herein, the authors discuss the use of self-assembled monolayers fabricated from the full membrane-spanning thiol (FMST) 3-((14-((4′-((5-methyl-1-phenyl-35-(phytanyl)oxy-6,9,12,15,18,21,24,27,30,33,37-undecaoxa-2,3-dithiahenpentacontan-51-yl)oxy)-[1,1′-biphenyl]-4-yl)oxy)tetradecyl)oxy)-2-(phytanyl)oxy glycerol for ultrahigh vacuum (UHV) based experiments. UHV-based methods such as electron spectroscopy and mass spectrometry can provide important information about how peptides bind and interact with membranes, especially with the hydrophobic core of a lipid bilayer. Near-edge x-ray absorption fine structure spectra and x-ray photoelectron spectroscopy (XPS) data showed that FMST forms UHV-stable and ordered films on gold. XPS and time of flight secondary ion mass spectrometry depth profiles indicated that a proline-rich amphipathic cell-penetrating peptide, known as sweet arrow peptide is located at the outer perimeter of the model membrane.
Relationships Among Coaching Success, Servant Leadership, Cohesion, Resilience and Social Behaviors
Authors: Gillham Andy , Gillham Eva , Hansen Keith
Published: February 2015

This study examined relationships among coaching success, servant leadership, team cohesion, athlete resilience and social behaviors utilizing responses from over 300 collegiate athletes. Horn’s (2008) model of coaching effectiveness served as the basis from which variables were operationalized and concurrently measured. Bivariate correlation analysis identified significant correlations among servant leadership and coaching success, cohesion and coaching success, cohesion and servant leadership, resilience and coaching success, and resilience and servant leadership, with most relationships moderate to weak. Canonical correlations were used to examine the data in greater depth and significant canonical variants revealed both expected and unexpected relationships. Multivariate analysis of variance results identified a significant main effect and seven significant follow-up analysis of variance tests. Athlete resilience, coach servant leadership and task-based team cohesion all varied significantly across the three levels of coaching success. Results of this study can be used by coaches, athletic administrators and coach educators for coach development.
First Human Case of Fatal Halicephalobus gingivalis Meningoencephalitis in Australia
Authors: Lim Chuan Kok , Crawford April , Moore Casey V. , Gasser Robin B. , Nelson Renjy , Koehler Anson V. , Bradbury Richard S. , Speare Rick , Dhatrak Deepak , Weldhagen Gerhard F.
Published: February 2015

Halicephalobus gingivalis(previouslyMicronema deletrix) is a free-living nematode known to cause opportunistic infections, mainly in horses. Human infections are very rare, but all cases described to date involved fatal meningoencephalitis. Here we report the first case ofH. gingivalisinfection in an Australian human patient, confirmed by nematode morphology and sequencing of ribosomal DNA. The implications of this case are discussed, particularly, the need to evaluate real-time PCR as a diagnostic tool.
Contribution of Neonatal Amniotic Fluid Testing to Diagnosis of Congenital Toxoplasmosis
Authors: Filisetti Denis , Yera Hélène , Villard Odile , Escande Benoît , Wafo Estelle , Houfflin-Debarge Véronique , Delhaes Laurence , Bastien Patrick
Published: February 2015

We evaluated the molecular diagnosis of congenital toxoplasmosis (CT) on neonatal amniotic fluid samples from 488 mother-child pairs. Maternal infection during pregnancy was diagnosed and dated or could not be ruled out. Forty-six cases of CT were defined according to the European Research Network on CT classification system and case definitions. Neonatal amniotic fluid testing had an overall sensitivity of 54% (95% confidence interval [95% CI], 39 to 69%) and a specificity of 100% (95% CI, 99 to 100%). Its sensitivity was 33% (95% CI, 13 to 59%) when antenatal diagnosis was positive and 68% (95% CI, 48 to 84%) when antenatal diagnosis was negative or lacking. This difference in sensitivity may have been due to treatment of antenatally diagnosed cases. Relative to postnatal serology, neonatal amniotic fluid testing allowed an earlier diagnosis to be made in 26% of the cases (95% CI, 9 to 51%).
Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry Meropenem Hydrolysis Assay with NH
4
HCO
3
, a Reliable Tool for Direct Detection of Carbapenemase Activity
Authors: Papagiannitsis Costas C. , Študentová Vendula , Izdebski Radoslaw , Oikonomou Olga , Pfeifer Yvonne , Petinaki Efthimia , Hrabák Jaroslav
Published: February 2015

A comparison of a matrix-assisted laser desorption ionization–time of flight mass spectrometric (MALDI-TOF MS) meropenem hydrolysis assay with the Carba NP test showed that both methods exhibited low sensitivity (approximately 76%), mainly due to the false-negative results obtained with OXA-48-type producers. The addition of NH
4
HCO
3
to the reaction buffer for the MALDI-TOF MS assay dramatically improved its sensitivity (98%). Automatic interpretation of the MALDI-TOF MS assay, using the MBT STAR-BL software, generally agreed with the results obtained after manual analysis. For the Carba NP test, spectrophotometric analysis found six additional carbapenemase producers.