bluuebunny/crossref_metadata_2025 huggingface dataset:
Mathematical Modeling of Within-Host Dynamics of Toxoplasma Gondii
Authors: Sullivan Adam , Zhao Xiaopeng , Su Chunlei
Published: May 2012

Toxoplasma gondii is a protozoan capable of replicating sexually in cats and asexually in other warm-blooded animals. By using a three dimensional mesh of both the brain and spleen, it is possible to simulate using a computational model to demonstrate the entire life-cycle within an intermediate host of the parasite as it completes the life-cycle using host cells of these organs. A cellular automata model is developed to demonstrate the dynamics of the parasite, where each cell follows the same set of rules for each discrete time-step. This cellular automata model allows for data simulations to be run of the parasite within a mouse and display graphical images and animations.
Hydropower Plant Frequency Control via Feedback Linearization and Sliding Mode Control
Authors: Ding Xibei , Sinha Alok
Published: May 2012

This paper presents a new nonlinear controller design approach for a hydraulic power plant focusing on Load Frequency Control aspect. It is based on input state feedback linearization and sliding mode/H∞ control. Simulation results for a nonlinear dynamic model of entire hydropower plant are presented and compared to those from the classical linear PI controller. A novel two-stage scheme for the nonlinear controller design with integral feedback is presented for a fast transient response and zero steady state error.
Coordinated Voltage Conversion and Low-Power Micro-Actuator Switching
Authors: Oldham Kenn , Edamana Biju , Hahn Bongsu
Published: May 2012

Due to very low power throughput and behavior as primarily capacitive loads, voltage conversion for micro-scale piezoelectric and electrostatic actuators can be very inefficient, while analog drive circuit supply currents may also exceed actuator power consumption. When limited instead to switching commands at discrete time instants to control micro-actuator motion, it may be advantageous to coordinate operating periods of any voltage conversion circuitry with actuators. A sample scenario of a traditional boost converter driving a thin-film piezoelectric micro-robotic appendage along a trajectory is considered through simulation studies. Some ranges of target motion accuracy are achieved using less energy, up to a 25% reduction at 30 V, for a 4 V battery, when coordinating voltage converter operation, even when conversion efficiency is very low.
Radial Basis Function Network (RBFN) Approximation of Finite Element Models for Real-Time Simulation
Authors: Narayanan Madusudanan Sathia , Singla Puneet , Garimella Sudha , Waz Wayne , Krovi Venkat
Published: May 2012

Nonlinearities inherent in soft-tissue interactions create roadblocks to realization of high-fidelity real-time haptics-based medical simulations. While finite element (FE) formulations offer greater accuracy over conventional spring-mass-network models, computational-complexity limits achievable simulation-update rates. Direct interaction with sensorized physical surrogates, in offline or online modes, allows a temporary sidestepping of computational issues but hinders parametric analysis and true exploitation of a simulation-based testing paradigm. Hence, in this paper, we develop Radial-Basis Neural-Network approximations, to FE-model data within a Modified Resource Allocating Network (MRAN) framework. Real-time simulation of the reduced order neural-network approximations at high temporal resolution provided the haptic-feedback. Validation studies are being conducted to evaluate the kinesthetic realism of these models with medical experts.
Active Control of Quazi-Zero Stiffness Isolators
Authors: Ahn Hyeong-Joon , Kim Kyoung-Rock
Published: May 2012

Various quasi-zero stiffness (QZS) passive vibration isolators were developed for protecting a system against vibration. This paper presents active control of a QZS vibration isolator. First, a unified model of QZS passive vibration isolators with symmetric nonlinearity is presented, which is a Duffing equation with odd power polynomials. Based the unified model, vertical and horizontal actuations are proposed for active control of QZS isolators. Finally, active control scheme for a QZS vibration isolator are presented and the isolation performances are compared with simulations.
Running Simulation Models in Parallel With Physical Systems for Improved Estimation Performance: Semantic Models Facilitate Updating Model State, Parameters, and Structure
Authors: Anand Dhananjay M. , Moyne James , Tilbury Dawn M.
Published: May 2012

When a simulation model for a dynamic system is used in parallel with the real physical system adaptation is a very important design feature. Model adaptation allows the model to compensate for errors between the simulated and real outputs. While parameter tuning and state updates can be automated to improve model accuracy, automatically updating the structure of a model is generally difficult to do. In order to build an automatic structural adaptation scheme we propose a semantic architecture for the model definition and use the semantic form to design an adaptation law. The semantic structure provides the standardization required for an automated algorithm to derive meaning from the model definition while allowing model designers to retain some generality in the way models are built. The semantic modeling approach is presented with an example implementation and discussion about its application to wide area distributed control systems. The wide area control system we use as motivation is a regional electrical power distribution controller.
MPC Based Integrated Chassis Control to Enhance Vehicle Handling Considering Roll Stability
Authors: Adireddy Ganesh , Shim Taehyun
Published: May 2012

An integrated vehicle chassis control system was developed to improve vehicle handling (yaw) responses while maintain vehicle roll stability using an 8 DOF vehicle model, a simplified tire model, and a model predictive control method. The proposed control system incorporates active wheel torque distribution, active front steering, and active anti-rollbar to enhance vehicle handling and its ability to track the desired trajectory when the risk of vehicle rollover is low. As vehicle rollover risks increase, the proposed control system shifts its control focus from only handling enhancement to vehicle roll stabilization by adjusting the gains in the controller. The simulation results show that the proposed control system can improve vehicle handling responses while ensuring vehicle roll stability at high speed vehicle maneuvers.
A Dual-Use Visible Light Communication and Orientation Estimation System for Underwater Robots
Authors: Rust Ian C. , Asada H. Harry
Published: May 2012

An integrated approach to underwater wireless communication and orientation estimation using visible light is presented and demonstrated using a simplified 1-DOF system. This system utilizes a long range, high bandwidth optical communication system as a reference with which to rectify error in the prediction of the orientation state. This is done through the use of a Discrete Kalman Filter. In this way, a dual-use system is developed. Using the same hardware, this system can simultaneously communicate using a modulated light source, and estimate, with accuracy, absolute orientation in space. This orientation knowledge is vital to maintaining a line-of-sight link for the communication system. In addition, orientation estimation is important for the various tasks that the underwater robot must perform.
De-Centralized and Centralized Control for EMS Maglev System Levitation and Guidance
Authors: Aly Mohamed , Alberts Thomas
Published: May 2012

The comparison between PD de-centralized and centralized control for an EMS maglev system that uses combined magnets with an inverted U-rail for levitation and guidance is presented. A simple 2-DOF maglev system model (rigid and flexible body cases) that comprises heave and lateral modes is used. The comparison is based on two aspects. First, by sketching the multi-input multi-output (MIMO) root loci with every controller individually for system rigid and flexible body cases. Second, a gradient-like search algorithm based on an optimal criterion for PD de-centralized and centralized controllers’ gains tuning is used. Simulation results of the maglev system with these tuned controllers show that the centralized control scheme is capable of lateral displacements suppression that may result from disturbing lateral forces than the de-centralized one.
Multi-Input Multi-Output Root Loci Analysis of EMS Maglev-Girder Interaction System
Authors: Aly Mohamed , Omran Ashraf , Alberts Thomas
Published: May 2012

A Maglev-girder interaction system experiences a variation of its dynamics as the vehicle’s position varies over the girder’s span at different speeds. This paper investigates this variation using Multi-input Multi-output root locus criteria. Thus, the change of the system’s poles and zeros is visualized with the change of the vehicle’s position, while the speed of the vehicle represents the rate of these changes. These Multi-input Multi-output root locus criteria are used to study and design both centralized and de-centralized controllers for Maglev system.
Analysis of Stability Control Systems for Single-Unit Commercial Vehicles
Authors: Horak Dan T.
Published: May 2012

The stability control problem of single-unit commercial vehicles, from large pickup trucks to motorcoaches, is analyzed. Detailed dynamic models of four baseline vehicles are used to estimate the feasibility and the performance limits of rollover stability and directional stability control systems for such vehicles on dry and wet roads.
A Control Approach for Broadening the Operating Frequency Range of a Bridge Vibration Energy Harvester
Authors: Pedchenko Alexander V. , Hoke Jonathan W. , Barth Eric J.
Published: May 2012

Remote bridge condition monitoring can be accomplished using sensors equipped with transmitters. This allows for timely detection of structural degradation and thereby increases safety. These sensors require a more permanent power source than batteries to enable operation without costly periodic maintenance. Since bridges exhibit structural vibration, electromagnetic vibration energy harvesting is a viable power source candidate. Unfortunately conventional electromagnetic vibration energy harvesters (VEHs) operate efficiently only at their natural frequency. Since a single bridge will vibrate differently, depending on its traffic conditions, the following work proposes a method for augmenting the excitation frequency bandwidth for electromagnetic VEHs, thereby enabling them to be feasible power supplies for bridge condition monitoring. Specifically, the paper provides experimental results showing the effectiveness of the proposed method in inducing resonance type behavior in an electromagnetic VEH at excitation frequencies that otherwise produce little to no motion in the harvester.
Stabilization of the Side Pull-In Bifurcation of an Electrostatic Comb Drive Actuator Model Using Oscillatory Open-Loop Control
Authors: Wickramasinghe I. P. M. , Berg Jordan M.
Published: May 2012

The stable operating region of an electrostatic comb drive actuator in constant-gap mode is limited by a subcritical pitch-fork bifurcation known as side pull-in. We show that oscillatory open-loop control can forestall side pull-in and substantially extend the stable operating region. To our knowledge, this is the first demonstration of control of side pull-in without additional lateral actuators. To our knowledge it is also the first application of open-loop oscillatory control to an electrostatic MEMS model using a single control voltage. Simulations show the stable range of travel increased by over 60%, with an associated oscillation of less than 2%. Although feedback control has been used to stabilize a related bifurcation in electrostatic gap-closing actuators, we show that these approaches are unlikely to succeed for side pull-in. Finally, we present and validate formulas relating parameters of the oscillatory input to the average value and oscillations of the resulting displacement.
Energy Harvesting, Ride Comfort, and Road Handling of Regenerative Vehicle Suspensions
Authors: Zuo Lei , Zhang Pei-Sheng
Published: May 2012

This paper presents a comprehensive assessment of the power that is available for harvesting in the vehicle suspension system and the tradeoff among energy harvesting, ride comfort, and road handing with analysis, simulations and experiments. The excitation from road irregularity is modeled as a stationary random process with road roughness suggested in the ISO standard. The concept of system H2 norm is used to obtain mean value of power generation and the root mean square values of vehicle body acceleration (ride quality) and dynamic tire-ground contact force (road handling). For a quarter car model, analytical solution of the mean power is obtained. The influence of road roughness, vehicle speed, suspension stiffness, shock absorber damping, tire stiffness, wheel and chasses masses to the vehicle performances and harvestable power are studied. Experiments are carried out to verify the theoretical analysis. The results suggest that road roughness, tire stiffness, and vehicle driving speed have great influence to the harvesting power potential, where the suspension stiffness, absorber damping, vehicle masses are insensitive. At 60mph on good and average roads 100–400 watts average power is available in the suspensions of a middle-size vehicle.
Stochastic Modelling of Drop Coalescence on Non-Porous Substrates for Inkjet Applications
Authors: Boley J. William , Sayer Robert A. , Chiu George T.-C.
Published: May 2012

Coalescence between two drops on a substrate is one of the important factors that can affect print quality in inkjet applications. Two stochastic models (constant contant angle mode and constant contact area mode) that consider drop placement error, drop impact, and drop evaporation are proposed for determining the probability of coalescence between adjacently printed drops on nonporous substrates. Experiments are conducted to measure the probability of coalescence with respect to deposition time difference between adjacently printed drops and compared to the predictions of the models. The measured coalescence follows the constant contact angle mode evaporation model during the initial phase of the life of the first drop, which is followed by a mix between the constant contact angle mode and the constant contact area mode models for the remainder of the life of the first drop. This study shows that for probabilities of coalescence between 10% and 80% the constant contact angle mode model can be used to determine deposition time difference threshold values for adjacent drops in applications promoting drop coalescence while the constant contact area mode model can be used for applications avoiding drop coalescence. Further efforts are needed to capture the dynamics of the mixed-model evaporation and to more accurately predict larger (greater than 80%) and smaller (less than 10%) occurrences of coalescence.
Diagnostics of Mechanical Faults of Loudspeakers Using Principal Component Analysis and Fisher’s Discriminant Analysis
Authors: Choi Jaewon , Bryant Michael D.
Published: May 2012

This study illustrates a novel model based FDI method for the common mechanical faults arising during the manufacture of loudspeakers. To overcome the drawbacks of the conventional signal based approaches, the Bayesian classification of impulse responses based on a model based fault symptom database is proposed. The loudspeaker model is estimated via IRES and ARMA techniques. The fault symptom database is constructed with a novel nonlinear loudspeaker model. The performances of Principal Component Analysis (PCA) and Fisher’s Discriminant Analysis (FDA) are compared. The results show the effectiveness of the proposed method. It is also shown that the FDA based classifier performs better than PCA in terms of the accuracy and consistency of the healthy baseline estimation. However, the fault isolation is difficult due to the similarities of fault signatures.
On the Effect of Pressure Oscillations on Droplet Autoignition
Authors: Eigenbrod Christian , Klinkov Konstantin , Fachini Fernando Filho
Published: May 2012

The paper discusses the possible interaction between combustion instabilities and induction times of droplets (and sprays) to autoignition. It is shown that acoustic pressure/temperature oscillations significantly affect the induction times of n-heptane droplets. This may play an additional role in low frequency dynamics and might be the main driver of high frequency dynamics. Experiments on single droplets in an acoustic field were used to validate numerical simulations on the autoignition of large n-heptane droplets. The simulations were then extended towards technical droplet sizes and a gas turbine typical pressure range of 17 bar. It was found that the acoustic-scale changes of the pressure and temperature result in significant changes of the ignition delay. Applying numerical calculations to micro-sized droplets enabled to study the thermo-acoustic effects under conditions approximating real gas-turbines. The findings reveal the importance of thermo-acoustic effects on ignition processes in the instability-driving mechanisms of combustion and indicate that “acoustics-ignition”-interactions must be taken into account for low-frequency as well as for high-frequency dynamics; this in addition to the flow and mixture perturbations which are well known to drive combustion instabilities in gas-turbines.
Life Estimation of TBC on an Aero Gas Turbine Combustor: A Finite Element Approach
Authors: Ragupathy R. , Mishra R. K. , Misal R. D.
Published: May 2012

Thermal barrier coatings (TBCs) are used for the thermal protection of turbine engine hot end components to have increased life and or better performance. Due to extreme environments and cyclic loads experienced by these components, the TBC may also fail prematurely. Once the TBC fails, it exposes the underlying substrate to very high gas temperatures and the life of the component gets reduced drastically and it can fail within its prescribed service life. This has necessitated the accurate possible estimation of TBC life. The TBC coated transition liner of an aero engine reverse flow combustion chamber has been analysed using finite element approach for life estimation. Stress analysis followed by fatigue analysis is carried out based on a typical mission cycle of the component for life estimation. The approach focuses on the mismatch in thermo-physical properties, operational conditions, Thermally Grown Oxide (TGO) layer surface finish and its growth. Increase in TGO thickness leads to decrease in life — this fact is modelled appropriately and proved using this FEM based methodology. Actual failure data of service engines has also been analysed and compared with that of predicted. This approach can be extended for parametric studies and life evaluation of any TBC system. The present approach will be adopted for qualification of prime reliant TBC for Aero engine application.
Adjoint-Based Flow Sensitivity Analyis Using Arbitrary Control Surfaces
Authors: Frey Christian , Ashcroft Graham , Backhaus Jan , Ku¨geler Edmund , Wellner Jens
Published: May 2012

This article describes how to extend the dsicrete adjoint method to functionals that are evaluated on arbitrary rotational control surfaces that intersect the flow domain at a position specified by the user, e.g. the pressure loss coefficient of a single blade in a multi-stage configuration. The definition and implementation of the mixed-out states on such surfaces is revisited. The calculation of the corresponding right-hand sides in the adjoint system is explained. These techniques can be used to specify functionals that quantify the deviation of the radial distribution of the flow angles, relative mass flow, etc. from a given target distribution. Sensitivity studies using the conventional approach, i.e. by means of finite differences of many steady solutions, are compared to results based on the adjoint method. The applications demonstrate that the agreement between adjoint and conventional sensitivity predictions is excellent, if the exact definition of the surface functionals is taken into account.
The Effect of Heat Generation on Low Cycle Fatigue Life Prediction
Authors: Scott-Emuakpor Onome , George Tommy , Cross Charles , Letcher Todd , Wertz John , Shen M.-H. Herman
Published: May 2012

An energy-based life prediction method is used in this study to determine the fatigue life of tension-compression loaded components in the very low cycle regime between 102 and 104. The theoretical model for the energy-based prediction method was developed from the concept that the strain energy accumulated during both monotonic failure and an entire fatigue process are equal; In other words, the scalar quantity of strain energy accumulated during monotonic failure is a physical damage quantity that correlates to fatigue as well. The energy-based method has been successfully applied to fatigue life prediction of components failing in the fatigue regime between 104 and 107 cycles. To assess Low Cycle Fatigue (LCF) with the prediction method, a clearer understanding of energy dissipation through heat, system vibration, damping, surface defects and acoustics were necessary. The first of these topics analyzed is heat. The analysis conducted studies the effect of heat generated during cyclic loading and heat loss from slipping at the interface of the grip wedges of the servo-hydraulic load frame and the test specimen. The reason for the latter is to address the notion that slippage in the experimental setup may be the cause of the reduction in the accuracy of the energy-based prediction method for LCF, which was seen in previous research. These analyses were conducted on Titanium 6Al-4V, where LCF experimental data for stress ratios R = −1 and R = −0.813 were compared with the energy-based life prediction method. The results show negligible effect on both total and cyclic energy from heat generation at the interface of the grip wedges and heat generation in the fatigue zone of the specimen.
Particle Transport Analysis of Sand Ingestion in Gas Turbine Engines
Authors: Brun Klaus , Nored Marybeth , Kurz Rainer
Published: May 2012

Significant interest exists in the military and commercial aerospace industry to be able to better predict and improve the durability of gas turbine jet engines that are operating in hostile desert environments, specifically, jet engines that see significant inlet sand or ash ingestion. This paper describes the development of a mixed CFD-empirical software tool that allows a detailed analysis of the kinematic and impact behavior of sand and other particulates in the near-field of turbomachinery blades and impellers. The tool employs a commercially available CFD solver to calculate the machine’s transient flow field and then uses the output to determine a set of non-dimensional coefficients in a set of empirical functions to predict the statistical probability of particles impacting on rotating or stationary surfaces. Based on this tool’s output information, improved inlet air filtering techniques, optimized engine maintenance practices, and component designs can be realized. To determine the empirical coefficient and to validate the method, PIV testing was performed on an airfoil in a wind tunnel, and then particle injection into a simple rotating impeller was tested on SwRI’s high-speed compressor test rig. Results from these tests allowed optimizing of the model to reflect rotating machinery particle impact behavior more accurately.
Wind Turbine Data Analytics for Drive-Train Failure Early Detection and Diagnostics
Authors: Yu LiJie
Published: May 2012

In recent years, rapid growth in wind energy as a substantial source of electricity generation has created greater demands on wind turbine system reliability and availability. To reduce service costs and maximize return on investment, wind farm operators have begun to take a more proactive approach to turbine problems by relying on intelligent condition monitoring and automated failure detection systems. The challenge is how to effectively convert large amounts of data into actionable decisions to detect and isolate failures at an early stage. This paper describes a unique data analysis and modeling technique for online turbine health monitoring and automatic root cause assessment. It provides a means to capture failure signatures for specific root causes based on historical events as well as engineering knowledge. Both continuous and discrete turbine condition monitoring data are processed to provide a failure probability assessment. First, statistical trend analysis, feature extraction and classification methods are developed to analyze a continuous sensor data set. Secondly, a pattern recognition method is applied to calculate failure indicators from various discrete control system events, or fault messages. Then failure likelihoods derived from both the continuous and the discrete models are combined in a fusion model to increase predictive accuracy. A demonstration of the method on bearing failure modeling using SCADA data will be provided with promising results.
Experimental and Numerical Investigation of Flow Field and Downstream Surface Temperatures of Cylindrical and Diffuser Shaped Film Cooling Holes
Authors: auf dem Kampe Tilman , Vo¨lker Stefan , Sa¨mel Torsten , Heneka Christian , Ladisch Helge , Schulz Achmed , Bauer Hans-Jo¨rg
Published: May 2012

An experimental and numerical study of the flow field and the downstream film cooling performance of cylindrical and diffuser shaped cooling holes is presented. The measurements were conducted on a flat plate with a single cooling hole with coolant ejected from a plenum. The flow field was investigated by means of 3D-PIV as well as 3D-LDV measurements, the downstream film cooling effectiveness by means of infrared thermography. Cylindrical and diffuser holes without lateral inclination have been examined, varying blowing ratio and density ratio as well as freestream turbulence levels. 3D-CFD simulations have been performed and validated along with the experimental efforts. The results, presented in terms of contour plots of the three normalized velocity components as well as adiabatic film cooling effectiveness, clearly show the flow structure of the film cooling jets and the differences brought about by the variation of hole geometry and flow parameters. The quantitative agreement between experiment and CFD was reasonable, with better agreement for cylindrical holes than for diffuser holes.
Performance of a Showerhead and Shaped Hole Film Cooled Vane at High Freestream Turbulence and Transonic Conditions
Authors: Newman A. , Xue S. , Ng W. , Moon H. K. , Zhang L.
Published: May 2012

An experimental study was performed to measure surface Nusselt number and film cooling effectiveness on a film cooled first stage nozzle guide vane using a transient thin film gauge (TFG) technique. The information presented attempts to further characterize the performance of shaped hole film cooling by taking measurements on a row of shaped holes downstream of leading edge showerhead injection on both the pressure and suction surfaces (hereafter PS and SS) of a 1st stage NGV. Tests were performed at engine representative Mach and Reynolds numbers and high inlet turbulence intensity and large length scale at the Virginia Tech Transonic Cascade facility. Three exit Mach/Reynolds number conditions were tested: 1.0/1,400,000; 0.85/1,150,000; and 0.60/850,000 where Reynolds number is based on exit conditions and vane chord. At Mach/Reynolds numbers of 1.0/1,450,000 and 0.85/1,150,000 three blowing ratio conditions were tested: BR = 1.0, 1.5, and 2.0. At a Mach/Reynolds number of 0.60/850,000, two blowing ratio conditions were tested: BR = 1.5 and 2.0. All tests were performed at inlet turbulence intensity of 12% and length scale normalized by the cascade pitch of 0.28. Film cooling effectiveness and heat transfer results compared well with previously published data, showing a marked effectiveness improvement (up to 2.5x) over the showerhead only NGV and agreement with published showerhead-shaped hole data. Net heat flux reduction was shown to increase substantially (average 2.6x) with the addition of shaped holes, with an increase (average 1.6x) in required coolant mass flow. Boundary layer transition location was shown to be within a consistent region on the suction side regardless of blowing ratio and exit Mach number.
Nonlinear Fault Diagnosis of Jet Engines by Using a Multiple Model-Based Approach
Authors: Naderi E. , Meskin N. , Khorasani K.
Published: May 2012

In this paper, a nonlinear fault detection and isolation (FDI) scheme that is based on the concept of multiple model (MM) approach is proposed for jet engines. A modular and a hierarchical architecture is proposed which enables the detection and isolation of both single as well as concurrent permanent faults in the engine. A set of nonlinear models of the jet engine in which compressor and turbine maps are used for performance calculations corresponding to various operating modes of the engine (namely, healthy and different fault modes) is obtained. Using the multiple model approach the probabilities corresponding to the engine modes of operation are first generated. The current operating mode of the system is then detected based on evaluating the maximum probability criteria. The performance of our proposed multiple model FDI scheme is evaluated by implementing both the Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF). Simulation results presented demonstrate the effectiveness of our proposed multiple model FDI algorithm for both structural and actuator faults in the jet engine.
Design Principles and Sizing Approach of Unfired Once-Through Steam Generators
Authors: Hamid E. , Newby M. , Pilidis P.
Published: May 2012

One of the key elements of increasing the thermal efficiency of a combined cycle power plant (CCPP) is to improve the design and operation of the heat recovery steam generators (HRSG) utilized in the cycle. Once-through steam generator (OTSG) is a new technology introduced for heat recovery in power systems. It eliminates boiler drums and other components of conventional HRSGs. The simplicity and compactness of an OTSG justifies its application in combined cycle power plants. This paper describes a design principle and an analytical sizing approach that will assist OTSG’s designers to achieve a good design by determining the core dimension, volume of an OTSG for given flow rates and their entering and leaving temperatures as well as the heat transfer area on the smoke side. The developed model has been tested with reference to a scaled model of an existing OTSG that is installed at Manx Electricity Authority and the results were promising. The overall characteristics of heat transfer and pressure drop distributions of the OTSG “scaled model” shows general agreement with the real characteristics of the existing OTSG with error values less than 1%.
Application of Dielectric Barrier Discharge to Improve the Flashback Limit of a Lean Premixed Dump Combustor
Authors: Versailles Philippe , Ali Chishty Wajid , Vo Huu Duc
Published: May 2012

In recent years, lean-premixed (LP) combustors have been widely studied due to their potential to reduce NOx emissions in comparison to diffusion type combustors. However, the fact that the fuels and oxidizers are mixed upstream of the combustion zone makes LP type of combustors a candidate for upstream flame propagation (i.e., flashback) in the premixer that is typically not designed to sustain high temperatures. Moreover, there has been a recent demand for fuel-flexible gas turbines that can operate on hydrogen-enriched fuels like Syngas. Combustors originally designed for slower kinetics fuels like natural gas can potentially encounter flashback if operated with faster burning fuels like those containing hydrogen as a constituent. There exists a clear need in fuel-flexible lean-premixed combustors to control flashback that will not only prevent costly component damage but will also enhance the operability margin of engines. A successful attempt has been made to control flashback in an atmospheric LP combustor, burning natural gas-air mixtures, via the application of Dielectric Barrier Discharge (DBD). A low-power DBD actuator was designed, fabricated and integrated into a premixer made out of quartz. The actuator was tuned to produce a low magnitude ionic wind with an intention to modify the velocity profile in the premixer. Flashback conditions were created by decreasing the air flow rate while keeping the fuel flow rate constant. Within this experimental setup, flashback happened in the core flow along the axis of the cylindrical premixer. Results show that the utilization of the DBD delays the occurrence of flashback to higher equivalence ratios. Improvements as high as about 5% of the flashback limit have been obtained without compromising the blowout limit. It is anticipated that this novel application of DBD will lead to future demonstrations of the concept under realistic gas turbine operating conditions.
Development of Key Technologies for the Next Generation High Temperature Gas Turbine
Authors: Ito Eisaku , Okada Ikuo , Tsukagoshi Keizo , Masada Junichiro
Published: May 2012

Global warming is being “prevented” by reducing power plant CO2 emissions. We are contributing to the overall solution by improving the gas turbine thermal efficiency for gas turbine combined cycle (GTCC). Mitsubishi Heavy Industries, Ltd. (MHI) is a participant in a national project aimed at developing 1700°C gas turbine technology. As part of this national project, selected component technologies are investigated in detail. Some technologies which have been verified through component tests have been applied to the design of the newly developed 1600°C J-type gas turbine.
Design and Optimization of a High Temperature Water Cooled Probe for Gas Analysis Measurement on K11 Combustion Test Rig
Authors: Plana Vincent , Vauthier Jean Se´bastien , Casteloot Cyril
Published: May 2012

DGA Aero-engine Testing offers an experience of more than 60 years in airbreathing engines testing. Components and especially combustion chambers are part of this experience from altitude simulated conditions to very high pressure and very high temperature requested for the next-generation engines. The K11, one of the most powerful combustion facilities worldwide, allows tests on full scale annular combustion chambers with a wide range of measurement devices. Its performance (100 kg/s, 60 bars, inlet 1073 K, outlet 2573 K) makes it a unique tool in the world for developing civil and military combustors. An internal traverse gear enables 360° mapping of combustor outlet, with pressure or temperature measurements and gas analysis (CO/CO2, UHC, NOx, Smoke Number) in accordance with ICAO and SAE standards. New probes have been designed and optimized to perform tests with an outlet combustor temperature up to (2123 K) with a high level of reliability in order to ensure the continuity of emissions measurement in the most severe conditions. The main results and the lessons learned during this study concerning the thermal and the structural behavior of the probe will be shown and discussed in this paper.
Protuberances in a Turbulent Thermal Boundary Layer
Authors: Mart Steven R. , McClain Stephen T.
Published: May 2012

Recent efforts to evaluate the effects of isolated protuberances within velocity and thermal boundary layers have been performed using transient heat transfer approaches. While these approaches provide accurate and highly resolved measurements of surface flux, measuring the state of the thermal boundary-layer during transient tests with high spatial resolution presents several challenges. As such, the heat transfer enhancement evaluated during transient tests are presently correlated to a Reynolds number based either on the distance from the leading edge or on the momentum thickness. Heat flux and temperature variations along the surface of a turbine blade may cause significant differences between the shapes and sizes of the velocity and thermal boundary layer profiles. Therefore, correlations are needed which relate the states of both the velocity and thermal boundary layers to protuberance and roughness distribution heat transfer. In this study, a series of three experiments are performed for various freestream velocities to investigate the local temperature details of protuberances interacting with thermal boundary layers. The experimental measurements are performed using isolated protuberances of varying thermal conductivity on a steadily-heated, constant flux flat plate. In the first experiment, detailed surface temperature maps are recorded using infrared thermography. In the second experiment, the unperturbed velocity profile over the plate without heating is measured using hot-wire anemometry. Finally, the thermal boundary layer over the steadily heated plate is measured using a thermocouple probe. Because of the constant flux experimental configuration, the protuberances provide negligible heat flux augmentation. Consequently, the variation in protuberance temperature is investigated using the velocity boundary layer parameters, the thermal boundary layer parameters, and the local fluid temperature at the protuberance apices. A comparison of results using plastic and steel protuberances illuminates the importance of the shape of the thermal and velocity boundary layers in determining the minimum protuberance temperatures.
Towards Surrogate Reaction Model Development
Authors: Slavinskaya N. A. , Zizin A. , Riedel U.
Published: May 2012

The present paper describes the proposed strategy of fuel model design based on identification of chemical and physical criteria for the selection of initial formula of the reference fuel. The first 8 criteria established and studied in previous papers so far are combustion enthalpy, formation enthalpy, molecular weight, C/H-ratio, sooting tendency index, critical point, two-phase diagram, and distillation curve. With these criteria established, the following candidate formula of the kerosene surrogate blend is defined and optimized to adequately mimic the properties of the real fuel: 10% n-propylcyclohexane, 13% iso-octane, 20% n-dodecane, 23% 1-methylnaphthalene, and 32% n-hexadecane. In this work, the ignition delay time has been studied as the next optimization criterion. To keep the model size small, the core reaction mechanism — the skeletal kinetics of n-heptane and iso-octane combustion including aromatics formation, developed earlier — is extended by n-propylcyclohexane, 1-methylnaphthalene, n-dodecane, and n-hexadecane sub-models. The lumped mechanisms for larger n-alkanes are constructed in a similar way to that for n-decane. The n-propylcyclohexane oxidation sub-model is derived from a skeletal mechanism for the low and high temperature cyclohexane oxidation. Reactions for 1-methylnaphthlene oxidation are included in the sub-mechanism for the formation of aromatics up to 5 ringed molecules. The mechanism includes 189 species and 1125 reactions. The proposed sub-models and overall mechanism are validated against experimental data obtained in shock tubes and in jet stirred reactor.s The simulations of ignition delay data for all hydrocarbons and their mixtures, i.e. for kerosene, are in good agreement with the measured data.
Prospects for Application of Ship’s Multi-Module Gas Turbine Engines on the Basis of Ceramic Tunnel Turbomachines
Authors: Sudarev A. V. , Suryaninov A. A. , Konakov V. G.
Published: May 2012

Analysis of thermodynamic and thermal-engineering parameters of GTE for mercantile and naval marines was conducted. A conclusion was made that GTEs designed specially for application under sea conditions have the highest efficiency. This is the 36–37% efficiency for simple cycle GTEs. With application of the complex cycle, a notable increase in the engine efficiency could be attained, particularly, by use of structural ceramics (SCMs) on the basis of innovative materials and some novel technological and design concepts. It permits to raise the engine efficiency up to 50% even with the net power of 300–500 kW. Results of numerical calculations for single unit and thirty two module GTEs demonstrated as follows. With the same baseline conditions, a multi-module unit has the volume which is more than twice less and the mass more than five times lower. Though when the number of GTE modules still further increases, decreasing of the turbomachine efficiency becomes a negative factor. To compensate it, it is required to increase the air heater regeneration ratio, to apply helical-channel turbomachines made of heat resistant SCMs, etc. Advantages of multi-module GTEs are evident. Thus, the mean efficiency of a machine during its lifetime increases. The handling independency increases, too. A need in outages to repair machines is eliminated. The control, governing and protection systems become simpler. The fire- and explosion safety increases. In fact, all the designing procedure now reduces to identification of the module number under conditions specified and within a space targeted. As opposed to a conventional ship’s GTE design with the engine having only a single electric net power generator, the multi-module design allows a fast implementation of the entire wide spectrum of operation duties required.
Numerical and Experimental Investigations of a Compressor Cascade Flow With Secondary Air Removal
Authors: Po¨nick Sascha , Kozˇulovic´ Dragan , Radespiel Rolf , Becker Bernd , Gu¨mmer Volker
Published: May 2012

The paper presents numerical and experimental results for a low speed compressor cascade with bleed air removal at the endwall. The aerofoil design is representative for a stator blade in a modern high pressure compressor near the casing wall. Secondary air is commonly supplied by simple bleed geometries downstream of stator rows. The focus of the present investigation was the systematic development of a passage integrated bleed configuration which, with the constraint of an invariable bleed mass flow rate, provides advantageous effect on the main flow and furthermore a high pressure recovery in the bleed flow. Steady 3D RANS simulations were performed using the Spalart-Allmaras turbulence model. In both, numerical simulations and experiments, an improved performance was found. Beside reduced losses and increased pressure rise the wake flow downstream of the customized bleed geometry was found to be more homogeneous with decreased deviations due to a favorable influence on the secondary flow.
Aerodynamics of a Centrifugal Compressor With a Double Sided Impeller
Authors: Lei Vai-Man
Published: May 2012

A double sided impeller, which consists of two impellers arranged in a back-to-back configuration with the backdisks eliminated, enables a single centrifugal compressor to have flow capacity similar to two compressors working in parallel but with a smaller packaging size. It reduces inertia of the rotating group and helps improve transient response. The smaller impeller diameter also enhances turbine performance by improving the compressor-turbine matching. These attributes are very attractive for automotive turbocharging applications. As a consequence of a common compressor inlet and diffuser, the two compressor sides interact and two operation modes exist. In the parallel mode, the two compressor sides work under comparable condition and the overall compressor behaves similar to a conventional compressor. As flow rate is reduced below a transition value, the system operates in a single-compressor mode with one compressor side flowing significantly more. The compressor side that flows more operates away from the stability limit and the side with low flow remains stable because of heavy recirculation flow with a ported shroud. Characteristics of the two operation modes are elucidated with test and CFD data.
Ship Propulsion Self-Excited Torsional Vibration
Authors: McAndrews Glenn , Murray Robert , Gemin Paul
Published: May 2012

Self-excited vibration is demonstrated in many common day events, for example, wheel-castor shimmy or a traffic sign twisting in a steady strong wind [1]. Another example, blade flutter, is well known in the gas turbine community. The affected system will typically oscillate at its natural frequency. When applied to propulsion shafting, the phenomenon produces significant levels of alternating torque that negatively affects the reliability of the drivetrain hardware. Starting with basic principles, this paper examines the conditions that can lead to self-excited torsional vibration. A screening parameter is developed that can be used to evaluate the potential for system instability. System stability mapping results are presented showing the effect of basic input parameters such as inertia, stiffness, and damping. The potential for self-excited torsional vibration is discussed in the context of recent trends in marine gas turbine propulsion (e.g. lightweight propulsors). Finally, countermeasures using the engine control system are outlined.
Controlled Fan Blade Tip/Shroud Rubs at Engine Conditions
Authors: Padova Corso , Dunn Michael , Barton Jeffrey , Turner Kevin , Steen Tod
Published: May 2012

The purpose of this paper is to describe the new facility design and operation improvements, and to demonstrate utility by providing typical results obtained as part of a typical measurement program. Since 2002 a number of experiments have been conducted to generate a broad database for tip rubs using two unique experimental facilities at the Gas Turbine Laboratory of The Ohio State University. Development of an in-ground spin-pit facility specifically designed to investigate rub-in-systems for jet engine components using real hardware rotating at representative engine speeds was reported several years ago. While the original smaller facility is still in use, more recently a much larger in-ground spin-pit facility for which the basic design and operation of the blade tip/shroud incursion technique is very different from the original facility design has been commissioned, and the results of a measurement program completed using a full-scale titanium-alloy fan blade rubbing an abradable casing are presented. The Large Spin-Pit Facility [LSPF] is designed to allow rotating engine hardware from low RPM [typically a few thousands] to 18,000 rpm, using two interchangeable spindle arrangements mounted above ground onto an in-ground containment tank. The LSPF is also designed to allow the progressive insertion of a casing segment into the path of a single-bladed or multiple-bladed disk. Segments extending 90 or 120 degrees are in use for different applications. For the configuration discussed in this paper, a 90-degree segment of a representative fan casing is forced to rub the tip of a titanium-alloy fan blade at a rotational speed in the vicinity of 6000 rpm.
Strategy for Selecting Optimised Technologies for Gas Turbine Air Inlet Filtration Systems
Authors: Hiner Stephen D.
Published: May 2012

With continuous advances in gas turbine technology, wider breadth of fuel quality burnt and ever growing expectations of; longer life, higher efficiency and reduced maintenance requirements, the filtration of the air entering the gas turbine (GT) has never been more important to meeting its operational requirements. Gas turbines are used throughout the world in an ever increasing diversity of application and environment. This presents a number of challenges to the air filtration system, that require unique solutions for each subset of environment specific challenge, gas turbine platform technology and fuel quality being burnt. This paper discusses the importance of air filtration to a modern GT and how this has changed over time and it’s shifting operational requirements. It explores the challenges facing the air filtration system presented by the different; environments, GT technologies and fuel quality. The paper details what approaches and filtration technologies are currently used to address these challenges, with strengths and weaknesses explained as appropriate, to finally present a strategy for specifying an optimized filtration system to meet the challenges of the modern GT.