bluuebunny/crossref_metadata_2025 huggingface dataset:
Safe Dynamic Operation of a Simple SOFC/GT Hybrid System
Authors: Stiller Christoph , Thorud Bjo̸rn , Bolland Olav
Published: November 2008

The current work shall prove the feasibility and show methods to safely operate a simple SOFC/GT hybrid system under part-load and load change. Dynamic and steady state studies on a detailed model of a SOFC/GT hybrid system have been performed. A design point is selected. Steady-state part-load behaviour is shown by means of performance maps. An operation line with fairly constant temperatures in the upper part-load regime and an almost constant efficiency down to app. 25% part-load is proposed and the dynamic behaviour of the system on rapid load changes is investigated. Strategies for the dynamic controlling of power by manipulating fuel flow are shown that might enable the system to adapt to a new setpoint power quite quickly.
Fiber-Optic Strain Gauge Calibration and Dynamic Flexibility Transfer Function Identification in Magnetic Bearings
Authors: Zutavern Zachary S. , Childs Dara W.
Published: November 2008

Historical attempts to measure forces in magnetic bearings (MBs) have experienced limited success as a result of relatively high uncertainties. Recent advances in strain-gauge technology have provided a new method for measuring MB forces. Fiberoptic strain gauges (FOSGs) are roughly 100 times more sensitive than conventional strain gauges and are not affected by electromagnetic interference. At the Texas A&M University (TAMU) Turbomachinery Laboratory, installing FOSGs in MBs has produced force measurements with low uncertainties. Dynamic flexibility transfer functions (DFTFs) exhibiting noticeable gyroscopic coupling have been identified and compared with finite element predictions. Comparison has verified the effectiveness of using MBs as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.
High Performance Condition Monitoring of Aircraft Engines
Authors: Herzog James P. , Hanlin Jason , Wegerich Stephan W. , Wilks Alan D.
Published: November 2008

A similarity-based modeling (SBM) technique is demonstrated that provides very early annunciation of the onset of gas path faults in aircraft engines. This powerful approach is shown to provide high fidelity estimates for real-time condition monitoring of aircraft engine signals. These estimates are used to detect the onset of changes in the inter-relationship between the various signals using a sophisticated set of built-in algorithms and tools. The ability of the SBM software to reliably detect subtle changes in signal behavior that are characteristic of a developing anomaly is coupled with a diagnostic rules engine to enable a rapid and robust fault recognition capability. The SBM software operates using a set of algorithms that construct a multivariate nonparametric model of the traditional monitoring sensors (pressure transducers, thermocouples, flow meters, etc.) present in the system. This model is used to generate real-time estimates of sensor values that represent normal system operation. A series of sophisticated tools compares these very high fidelity estimates to the actual sensor readings to detect discrepancies. Finally, a series of logic rules derived from a combination of engineering analysis and experience is applied to the output from the modeling engine in real-time to alert the user of developing serious conditions that need either immediate or planned maintenance attention. The software system provides a complete approach to asset monitoring that minimizes down time, maximizes availability, encodes (preserves) operator knowledge and lowers the overall costs associated with maintaining the assets. In this paper, we demonstrate the use of the similarity-based modeling approach for detecting faults in the gas path of aircraft engines. Some results from the monitoring of over 1,100 engines at a major commercial airline over a two-year period are described. Operationally, the early detection of developing engine faults has prevented delays and cancellations, and has contributed to a reduction in the airline’s in-flight shutdown rate. Financially, this approach has led to significant cost savings by the prevention of major secondary damage.
Heavily Loaded Gas Foil Bearings: A Model Anchored to Test Data
Authors: Kim Tae Ho , San Andre´s Luis
Published: November 2008

Widespread usage of gas foil bearings (FBs) into micro turbomachinery to midsize gas turbine engines requires accurate performance predictions anchored to reliable test data. The paper presents a simple yet accurate model predicting the static and dynamic force characteristics of gas FBs. The analysis couples the Reynolds equation for a thin gas film to a simple elastic foundation model for the top foil and bump strip layer. An exact flow advection model is adopted to solve the partial differential equations for the zeroth- and first- order pressure fields that render the FB load capacity and frequency dependent force coefficients. As the static load imposed on the foil bearing increases, predictions show the journal center displaces to eccentricities exceeding the bearing nominal clearance. A nearly constant FB static stiffness, independent of journal speed, is estimated for operation with large loads; and approaching closely the structural stiffness derived from contact operation at null rotor speed. Predicted minimum film thickness and journal attitude angle demonstrate good agreement with archival test data for a first-generation gas FB. The bump-foil strip structural loss factor, exemplifying a dry-friction dissipation mechanism, aids to largely enhance the bearing direct damping force coefficients. At high loads, the bump-foil structure influences most the stiffness and damping coefficients. The FB whirl frequency ratio (WFR) is examined to ensure its dynamically stable operation. The predictions demonstrate that FBs have greatly different static and dynamic force characteristics when operating at journal eccentricities in excess of the bearing clearance from those obtained for operation at low loads, i.e. small journal eccentricities.
Test results of the OGT2500 Gas Turbine Engine Running on Alternative Fuels: BioOil, Ethanol, BioDiesel and Crude Oil
Authors: Lupandin Vladimir , Thamburaj Raj , Nikolayev Alexander
Published: November 2008

This paper describes the results of an on going development program aimed at determining the technical feasibility of utilizing alternative fuels such as bio-mass derived BioOil, Ethanol, Bio-Diesel and bituminous Crude Oil in a 2.5 MW GT2500 industrial Gas Turbine Engine. This gas turbine engine was designed and manufactured by “Zorya-Mashproekt” in the Ukraine and further modified for the alternative fuels application through a join development program between “Zorya-Mashproekt” and Orenda Aerospace Corporation in Canada. The modification of the GT2500 Gas Turbine Engine hot section and combustion system to operate on liquid alternative fuels are described. Also described is an engine hot section online cleaning system and features of the fuel-handling module, which carries out fuel preheating and preprocessing. A test rig equipped with a load bank was designed and built to test the modified GT2500 Gas turbine Engine on different alternative fuels (full speed/full power). Results of the modified GT2500 gas turbine engine operation along with the emissions data are presented. The tests proved the technical feasibility of operating this gas turbine engine on the alternative fuels mentioned above. Based on these results a power generation package with the engine and fuel handling module have been accepted for commercial operation in a pilot plant under construction in West Lorne, Ontario, Canada.
Application of a Constant Gain Extended Kalman Filter for In-Flight Estimation of Aircraft Engine Performance Parameters
Authors: Kobayashi Takahisa , Simon Donald L. , Litt Jonathan S.
Published: November 2008

An approach based on the Constant Gain Extended Kalman Filter (CGEKF) technique is investigated for the in-flight estimation of non-measurable performance parameters of aircraft engines. Performance parameters, such as thrust and stall margins, provide crucial information for operating an aircraft engine in a safe and efficient manner, but they can not be directly measured during flight. A technique to accurately estimate these parameters is, therefore, essential for further enhancement of engine operation. In this paper, a CGEKF is developed by combining an on-board engine model and a single Kalman gain matrix. In order to make the on-board engine model adaptive to the real engine’s performance variations due to degradation or anomalies, the CGEKF is designed with the ability to adjust its performance through the adjustment of artificial parameters called “tuning parameters.” With this design approach, the CGEKF can maintain accurate estimation performance when it is applied to aircraft engines at off-nominal conditions. The performance of the CGEKF is evaluated in a simulation environment using numerous component degradation and fault scenarios at multiple operating conditions.
Evaluation of Emissions Performance of Existing Combustion Technologies for Syngas Combustion
Authors: Iyer Venkatraman , Haynes Joel , May Patrick , Anand Ashok
Published: November 2008

Syngas is composed of mixtures of H2 and CO and inerts such as N2, steam and CO2. The composition of syngas derived from oxygen and air-blown gasifiers is discussed. The low exhaust gaseous emissions potential of diffusion, lean premixed and rich catalytic combustors with representative oxygen and air-blown syngas fuels are evaluated. The evaluation is performed using network of well-stirred reactor models. The parameters of the reactor models are carefully chosen so as to represent the flow-physics in the combustors. Predictions of NO and CO emissions for the different combustion modes are presented for the representative syngas fuels. The calculations are performed with combustor pressures and inlet temperatures typical of heavy-duty gas turbine power generation plants. The effect of combustor exit temperature, added diluents and the composition of the fuel on NO and CO emissions are evaluated for the different combustion technologies. The sensitivity of the emissions to reactor parameters is also explored.
High Frequency Incipient Fault Detection for Engine Bearing Components
Authors: Kallappa Pattada , Byington Carl S. , Kalgren Patrick W. , DeChristopher Michael , Amin Sanket
Published: November 2008

This paper investigates the feasibility of using contact and non-contact sensors to develop an ultra high frequency (UHF) vibration monitoring system for prognostics/diagnostics of turbine engine bearings. The authors have developed ImpactEnergy™, a feature extraction and analysis driven system that integrates high frequency vibration/acoustic emission data, collected using accelerometers and a laser interferometer to assess the health of bearings and gearboxes in turbine engines. ImpactEnergy™ combines advanced diagnostic features derived from waveform analysis, high-frequency enveloping, and more traditional time domain processing like root mean square (RMS) and kurtosis with classification techniques to provide bearing health information. The intelligent UHF concepts based system (System) presented in this paper is tested and validated in a laboratory environment by monitoring multiple bearings on test rigs that replicate the operational loads of a turbomachinery environment. The UHF system is also applied to data collected on test rigs at original equipment manufacturer (OEM) locations.
Ignition of Lean Methane-Based Fuel Blends at Gas Turbine Pressures
Authors: Petersen Eric L. , Hall Joel M. , Smith Schuyler D. , de Vries Jaap , Amadio Anthony , Crofton Mark W.
Published: November 2008

Shock-tube experiments and chemical kinetics modeling were performed to further understand the ignition and oxidation kinetics of lean methane-based fuel blends at gas turbine pressures. Ignition delay times were obtained behind reflected shock waves for fuel mixtures consisting of CH4, CH4/H2, CH4/C2H6, and CH4/C3H8 in ratios ranging from 90/10 to 60/40%. Lean fuel/air equivalence ratios (φ = 0.5) were utilized, and the test pressures ranged from 0.54 to 25.3 atm. A methane-oxidation kinetics mechanism based on GRI-Mech 3.0 was assembled to reproduce the methane/air mixtures. Additional reactions involving CH3O and CH3O2 chemistry and modifications to a few of the pressure-dependent reaction rate coefficients were needed to achieve good agreement between data and model.
Characterization and Reduction of Pollutant Emissions From a Landfill and Digester Gas Fired Mictroturbine Generator
Authors: Effinger Mark , Mauzey Josh , McDonell Vince
Published: November 2008

Distributed Generation (DG), where small-scale power generation capacity is installed at or near its point of use, is of growing interest to reduce the need for the addition of traditional, large, centralized power plants. Microturbine generators (MTGs) represent one type of DG platform, applications for which continue to expand as the technology improves. MTGs have already shown flexibility in operation on alternatives fuels, making them a potential candidate for use in the renewable energy market. However, many renewable fuels, such as gases produced at wastewater treatment plants and landfills, have significantly lower heating values than pure natural gas. Due to lower volumetric energy content, these waste gases are commonly referred to as medium-BTU fuels. While examples of MTGs operating on these renewable fuels grow in number, little detailed information on the systematic effect of fuel composition on MTG performance is available. The current study characterizes emissions performance of a commercial natural gas fired MTG operating on medium-BTU fuel and identifies the relationship between fuel composition and emissions performance over a 50 to 100% load profile. Results from the implementation of a new injector designed to reduce emissions are also presented.
A Conceptual Design of a Polymer-Derived Ceramic Hot-Wire Anemometer for Gas Turbine Environment
Authors: Nagaiah N. R. , Krishnan V. , Kapat J. S. , An L.
Published: November 2008

This paper attempts to prove the feasibility of high temperature hot-wire anemometer for gas turbine environment. No such sensor exists at present. Based on the latest improvement in a new type of Polymer-Derived Ceramic (PDC) material, the authors present a conceptual design of a hot-wire anemometer (HWA) based on PDC material, and show that such a sensor is indeed feasible. This HWA is microfabricated by using three types of PDC materials such as SiAlCN, SiCN (lightly doped) and SiCN (heavily doped) for sensing element (hot-wire), support prongs and connecting leads respectively. The PDC-SiAlCN is selected as a sensing element, because of its high temperature coefficient of resistance (4000 ppm/°C) and resistivity. Direct measurements and characterization of the relevant material properties are presented, to show that the proposed design can lead to a viable constant temperature anemometer. In our current design, the hot wire is 200μm in length and 20 μm × 20 μm side. Analysis of the sensor performance is used to predict sensor response behavior, and the systematic analysis of this new device, especially the steady state characteristics, frequency response and directional dependence are discussed. This novel hot wire anemometer is found to perform quite satisfactorily as compared to a conventional HWA in which the hot wire is made of Pt/W/Pt-Ir. Sensor output is predicted to be in the range of 10 to 50 V (without additional signal conditioning) for velocities in the range of 10 to 100 m/s. The sensitivity of the sensor is found to be better than a conventional sensor: 0.157 V/(m/s) (for sensor length of 0.2 mm) vs 0.014 V/(m/s) respectively at 50 m/s. However, L/d ratio may need to be limited to about 10 so that output voltage is not excessive, thus requiring careful consideration of support conduction during calibration. This type of PDC-HWA can be used in harsh environment due to its high temperature resistance, tensile strength and resistance to oxidation. This paper also discusses micro-stereolithography as a novel microfabrication technique to manufacture the proposed PDC-HWA.
3D Simulation of a Convergent-Divergent Aero Engine Intake, Using Two Different CFD Methods
Authors: Templalexis Ioannis , Pilidis Pericles , Guindeuil Geoffrey , Lekas Theodoros , Pachidis Vassilios
Published: November 2008

This study refers to the development and validation of a Three Dimensional (3D) Vortex Lattice Method (VLM) to be used for internal flow case studies and more precisely aero-engine intake simulation. It examines the quantitative and qualitative response of the method to a convergent – divergent intake, produced as a surface of revolution of the CFM56-5B2 upper lip geometry. The study was carried out for three different sections namely: Intake outlet, intake throat and intake inlet. Moreover five different settings of Angle Of Attack (AOA) were considered. The VLM was based on an existing code. It was modified to accommodate internal flow effects and match, as closely as possible, the boundary conditions set by the Reynolds Average Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) simulation. In the context of this study, Vortex Lattice-derived average values velocity profiles were compared against RANS CFD results.
Aero Engine Axi-Symmetric Convergent-Constant Area Intake 3D Simulation Using a Panel Method Approach
Authors: Templalexis Ioannis , Pilidis Pericles , Guindeuil Geoffrey , Kotsiopoulos Petros , Pachidis Vassilios
Published: November 2008

This study has been carried out as a part of a general effort to develope a powerful simulation code, based on the Vortex Lattice Method (VLM), capable of simulating adequately accurate and comparatively fast, internal flow regimes. It utilizes a convergent – (nearly) constant area axi-symmetric intake three dimensional geometry, emerged as a surface of revolution from the CFM56-5B2 lower lip geometry. The study focuses on the three most critical planes, which are the inlet of the intake, the outlet of the diverging section and the outlet of the intake. Moreover, the sensitivity of the simulation on the variation of the Angle Of Attack (AOA) is tested for four different settings equally spaced, ranging from 0 to 20 degrees. The comparison is carried out on both two-dimensional velocity distributions and average values. The VLM simulation code was based on an existing code, which was modified in order to be adapted to the Reynolds Average Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) boundary conditions.
Comparative Performance Assessment of Pressurized Solid Oxide Fuel Cell/Gas Turbine Hybrid Systems Considering Various Design Options
Authors: Yang Won Jun , Kim Tong Seop , Kim Jae Hwan , Sohn Jeong L. , Ro Sung Tack
Published: November 2008

This study aims at presenting important aspects in developing the pressurized SOFC/GT hybrid system, such as different types of system configurations, characteristics of matching between SOFC and GT and effects of design constraints. Assorted system configurations, depending on component design technologies, are analyzed and their performances are comparatively evaluated. Various options considered are internal and external reforming processes, reforming steam supply methods and reforming heat sources. Performances are examined in terms of matching of cell temperature and turbine inlet temperature. Performance limitation caused by practical matching of those parameters under additional constraints on the cell stack (temperature difference at the cell) is investigated. Performances of the hybrid systems are also compared with those of the SOFC only systems under identical constraints and the extent of performance enhancement is evaluated. In order for the system to reach a comparable level of efficiency with internal reforming, the system having external reforming requires both high operating temperature of the cell and large temperature difference at the cell. With a practical design constraint, the internally reformed system is more efficient and this superiority becomes increasingly evident as the constraint becomes more severe.
How to Create a Performance Model of a Gas Turbine From a Limited Amount of Information
Authors: Kurzke Joachim
Published: November 2008

Gas turbine manufacturers develop complex performance simulation models for their products; these proprietary models are based on design information and the many measurements taken during engine development. For subcontractors in collaborative projects, for gas turbine users and outsiders there is often only a limited amount of data accessible for creating a performance model of the engine. User-friendly, accurate and fast PC-based engine simulation tools are available for anybody from several sources. With these tools it is possible to create from a limited amount of data full thermodynamic models. In this paper a methodology is presented which minimizes the effort needed for creating such models. It consists of four steps: Firstly a suitable cycle reference point is chosen and the model is tailored to the data of this point. Secondly compressor and turbine maps are added and scaled such that they fit exactly to the cycle reference point. In this step a second operating point is considered and the location of the cycle reference point in the component maps is adapted such that the simulation fits optimally to the given data of the second point. In a third step, the rest of the data are compared graphically with the simulation. Here many modelers fall in a trap: They plot the data versus spool speed as x-axis because speed is accurately measurable and regarded as reliable information. However, spool speed is — from the view of thermodynamics — a parameter of secondary importance. If the correlation of spool speed with corrected flow in the compressor map is incorrect — which is very probable at the beginning of the modeling process — then all graphics will show discrepancies. This makes the adaptation of the model to the data an extended iterative process. If one uses for the model checks a primary thermodynamic parameter — like corrected mass flow, overall pressure ratio or thrust respectively shaft power — as basis then the task is very much simplified. In the fourth and final step the speed values in the estimated compressor maps are adjusted. This has little effect on the matching accuracy of the previous steps, so the model is finished quickly. The procedure is demonstrated by creating a model for a two-spool turbojet which was tested over quite a range of operating conditions in an altitude test facility. Without much iteration a model is quickly created which matches all the measured data within the quoted uncertainty of the measurements.
Comparison of Combustion Properties Between a Synthetic Jet Fuel and Conventional Jet A1
Authors: Hermann Fredrik , Hedemalm Per , Orbay Raik , Gabrielsson Rolf , Klingmann Jens
Published: November 2008

Aviation fuel is a petroleum product that fulfills the Standard Specification for Aviation Turbine Fuels. Crude oil has been the raw material for production of aviation fuels for many years. Since the availability of crude oil is predicted to be limited in the future, alternative raw materials for aviation fuels are highly desirable. A Swedish company, Oroboros AB, has developed a novel clean synthetic jet fuel, LeanJet®. The fuel is produced synthetically from synthesis gas (Syngas) by the Fischer-Tropsch process. A comparative experimental investigation of combustion properties has been performed, comparing the synthetic jet fuel with Jet A1. The following parameters were investigated in an atmospheric combustor, which was originally designed for a Volvo Aero turbine (VT40): • Emissions of NOx, CO and HC; • Ignition and extinction points; • Liner temperatures; • Soot levels in the combustor. The emission measurements showed good combustion efficiency with low HC and CO for both fuels. With very lean mixtures, however, both the CO and the HC levels increased for the synthetic fuel. The nitrous oxides for the synthetic jet fuel were reduced over the operation conditions investigated. Qualitative reduction of soot levels was also seen for the synthetic jet fuel. The fuels showed no difference in material temperature along the combustor wall. Small differences in ignition characteristics were found, but no differences in extinction were observed.
Micro Gas Turbine Repowering With Inverted Brayton Cycle
Authors: Bianchi M. , De Pascale A. , Negri di Montenegro G.
Published: November 2008

Micro gas turbine may represent a successful energy system for distributed combined heat and power generation, if its energetic and economic performances become competitive, especially in cogenerative application. Furthermore, in the last years, the Inverted Brayton Cycle gas turbine has been reconsidered as a potential solution for the simple cycle gas turbine performance increase. In the present paper, the employment of an Inverted Brayton Cycle at the micro gas turbines discharge is investigated. The results obtained show that the electric and thermal performances of the energy system increase; moreover, the reduction of the maximum hot gas temperature in the recuperator (usually micro gas turbines are recuperated), due to the below ambient pressure expansion, may reduce the recuperator thermal stress problems. The economic impact of the repowering of simple cycle micro gas turbines with the Inverted Brayton Cycle is also investigated in the present study; the carried out analysis shows that the benefit of the Inverted Brayton Cycle depends on the fuel price and the electric energy tariff and the turbine discharge pressure can be optimized to maximize the economic performance.
Influence of Contact States on the Dynamic Behavior of Rubbing Structures
Authors: D’Ambrosio Flavio , Chatelet Eric , Jacquet Georges
Published: November 2008

One of the most common failure modes for turbomachinery wheels is associated to high-cycle fatigue of blades. A classical way to extend the working life of those structures is obtained through the introduction of specific devices in order to reduce vibrational amplitudes during resonance. Different kinds of components are used such as shrouds and wires within power industry and under platform limiters for aeronautics. Dry friction between the devices and blades induces non linear behaviors and flattens the associated frequency response functions (FRF). Even if this phenomena is now well known, different interpretations are presented in bibliography to explain the origin of this flattening. The most common one is based on the dissipated energy while more recent studies propose a different approach and explain peak flattening by changes in boundary conditions induced by the stick/slip phenomenon. The objective of the proposed study is to progress towards a better understanding of the flattening phenomena during vibration of bladed assemblies in presence of dry friction. A simple case is analyzed in order to show the contribution of respectively energy dissipation and changes of contact state on peak levels.
Flame Characteristics and Turbulent Flame Speeds of Turbulent, High-Pressure, Lean Premixed Methane/Air Flames
Authors: Griebel P. , Bombach R. , Inauen A. , Scha¨ren R. , Schenker S. , Siewert P.
Published: November 2008

The present experimental study focuses on flame characteristics and turbulent flame speeds of lean premixed flames typical for stationary gas turbines. Measurements were performed in a generic combustor at a preheating temperature of 673 K, pressures up to 14.4 bars (absolute), a bulk velocity of 40 m/s, and an equivalence ratio in the range of 0.43–0.56. Turbulence intensities and integral length scales were measured in an isothermal flow field with Particle Image Velocimetry (PIV). The turbulence intensity (u′) and the integral length scale (LT) at the combustor inlet were varied using turbulence grids with different blockage ratios and different hole diameters. The position, shape, and fluctuation of the flame front were characterized by a statistical analysis of Planar Laser Induced Fluorescence images of the OH radical (OH-PLIF). Turbulent flame speeds were calculated and their dependence on operating conditions (p, φ) and turbulence quantities (u′, LT) are discussed and compared to correlations from literature. No influence of pressure on the most probable flame front position or on the turbulent flame speed was observed. As expected, the equivalence ratio had a strong influence on the most probable flame front position, the spatial flame front fluctuation, and the turbulent flame speed. Decreasing the equivalence ratio results in a shift of the flame front position farther downstream due to the lower fuel concentration and the lower adiabatic flame temperature and subsequently lower turbulent flame speed. Flames operated at leaner equivalence ratios show a broader spatial fluctuation as the lean blow-out limit is approached and therefore are more susceptible to flow disturbances. In addition, because of a lower turbulent flame speed these flames stabilize farther downstream in a region with higher velocity fluctuations. This increases the fluctuation of the flame front. Flames with higher turbulence quantities (u′, LT) in the vicinity of the combustor inlet exhibited a shorter length and a higher calculated flame speed. An enhanced turbulent heat and mass transport from the recirculation zone to the flame root location due to an intensified mixing which might increase the preheating temperature or the radical concentration is believed to be the reason for that.
Design and Development Test of a Gas Turbine Combustor for High Hydrogen Medium Heating Value Syngas Fuel
Authors: Xu Gang , Cui Yufeng , Yu Bin , Lei Yu , Nie Chaoqun , Xiao Yunhan , Huang Weiguang
Published: November 2008

When gas turbine is used in coal co-production system, its combustor needs to burn syngas produced by coal gasification. The syngas’ main combustible compositions are CO and H2, and it has a nominal lower heating value of 10920kJ/ncm. In this paper, three modification schemes of a heavy-duty gas turbine combustor burning syngas are proposed. Flow fields, temperature profile and chemical reaction characteristics are compared using three-dimensional CFD numerical simulation and two of them have been chosen for medium-pressure, full-scale tests at the Gas Turbine Combustor Laboratory of the Institute of Engineering Thermophysics, Chinese Academy of Sciences. Laboratory tests show good result in exhaust emissions, combustor efficiency, exhaust temperature profile, and metal temperature distribution of liner and transaction pieces, which indicate that the retrofitting schemes satisfied the design specification. In addition, the dynamic characteristics of the combustors are researched applying FFT and wavelet analyses.
Carbon-Free Hydrogen and Electricity From Coal: Options for Syngas Cooling in Systems Using a Hydrogen Separation Membrane Reactor
Authors: De Lorenzo Luca , Kreutz Thomas G. , Chiesa Paolo , Williams Robert H.
Published: November 2008

Conversion of coal to carbon-free energy carriers, H2 and electricity, with CO2 capture and storage may have the potential to satisfy at a comparatively low cost much of the energy requirements in a carbon-constrained world. In a set of recent studies, we have assessed the thermodynamic and economic performance of numerous coal-to-H2 plants that employ O2-blown, entrained-flow gasification and sour water-gas shift (WGS) reactors, examining the effects of system pressure, syngas cooling via quench versus heat exchangers, “conventional” H2 separation via pressure swing adsorption (PSA) versus novel membrane-based approaches, and various gas turbine technologies for generating co-product electricity. This study focuses on the synergy between H2 separation membrane reactors (HSMR) and syngas cooling with radiant and convective heat exchangers; such “syngas coolers” invariably boost system efficiency over that obtained with quench-cooled gasification. “Conventional” H2 separation requires a relatively high steam-to-carbon ratio (S/C) to achieve a high level of H2 production, and thus is well matched to relatively inefficient quench cooling. In contrast, HSMRs shift the WGS equilibrium by continuously extracting reaction product H2, thereby allowing a much lower S/C ratio and consequently a higher degree of heat recovery and (potentially) system efficiency. We first present a parametric analysis illuminating the interaction between the syngas coolers, high temperature WGS reactor, and HSMR. We then compare the performance and cost of six different plant configurations, highlighting: 1) the relative merits of the two syngas cooling methods in membrane-based systems, and 2) the comparative performance of “conventional” versus HSMR-based H2 separation in plants with syngas coolers.
Impact of Multiple On-Board Inspections on Cumulative Probability of Detection
Authors: Shook Brian D. , Millwater Harry R. , Enright Michael P. , Hudak Stephen J. , Francis William L.
Published: November 2008

The impending application of on-board sensors for detecting and sizing material defects and evaluating their consequences will lead to improved forecasting of readiness, as well as improved safety, retirement-for-cause, and management of assets. This research looks at the consequences of multiple, i.e., continual, on-board inspections on the cumulative probability of detection (CPOD) of the system; that is the probability of detecting a defect considering all previous inspections. In particular, modeling and simulation of the CPOD is examined as a function of the degree of correlation between subsequent inspections. A surface crack in a turbine disk is used as a test case with loading from a typical stress spectrum from a fighter engine. The analysis indicates that a significant difference in detectability is achieved through multiple inspections depending upon the degree of correlation between inspections, with statistically independent inspections exhibiting a “dramatically” improved CPOD over dependent inspections. In particular, if each inspection is statistically independent 1) it is the left tail of the parent POD that defines the CPOD, 2) for the same median value, a higher coefficient of variation of the parent POD generates a significantly more effective CPOD, and 3) if enough inspections are performed, the CPOD curve becomes a step function at the first non-zero value in the parent POD curve, thereby giving orders-of-magnitude improvement in detectibility over the parent POD. The critical issue of statistical independence of multiple inspections is investigated by examining the CPOD as a function of correlation between inspections. The results indicate that the effectiveness of continual inspections on the CPOD varies from a correlation coefficient of zero (independent), which gives a dramatic improvement compared to the parent POD, to a correlation coefficient of one (dependent), which reverts to the parent POD. In summary, the correlation between inspections is a critical component that determines the effectiveness of continual inspections.
Automated Contingency and Life Management for Integrated Power and Propulsion Systems
Authors: Kallappa Pattada , Hailu Haftay
Published: November 2008

Impact Technologies, LLC has developed a prototype Automated Contingency and Life Management (ACLM) System for aircraft propulsion systems. Using a combination of on-board diagnostic and control modules, the ACLM system implements real-time and near real-time strategies to detect critical and life limiting engine faults and take appropriate control actions to ensure optimal performance. The modular hierarchical ACLM architecture is populated with Prognostics and Health Monitoring (PHM), and Adaptive Intelligent Control (AIC) algorithms. The PHM algorithms include Statistical Fault Pattern Recognition, Probabilistic Neural Network and Model-Based modules. These algorithms work in parallel and their outcomes are fused to provide a comprehensive fault diagnosis with an associated level of confidence. The AIC consists of a hierarchical framework for the implementation of the control strategy. The strategy incorporates varying control modes, such as life extending, performance and safe/abort/contingency management. This ACLM system has been demonstrated on an Air Force Research Laboratory generic two-spool turbofan engine computer simulation model.
Acoustic Based Rapid Blowout Mitigation in a Swirl Stabilized Combustor
Authors: Prakash Shashvat , Nair Suraj , Muruganandam T. M. , Neumeier Yedidia , Lieuwen Tim , Seitzman Jerry M. , Zinn Ben T.
Published: November 2008

This paper describes a method for efficiently detecting and preventing lean blow out (LBO) in a premixed, swirl stabilized combustor. The acoustic signal is processed to determine the real time LBO probability. This requires detection of localized extinction ‘events’ and rapid calculation of event frequency. As LBO probability increases, a proportional derivative controller actuates valves to redirect a fraction of the total fuel into a central, premixed pilot. The actuation increases the equivalence ratio in the stabilization region at a constant power setting and counters the flame lift associated with LBO. It is shown that the developed controller can prevent LBO even during rapid transients in equivalence ratio, φ.
Test Protocols for Combustion Turbine Inlet Cooling Foggers
Authors: Levine Philip , Angello Leonard C.
Published: November 2008

This paper on test protocols for combustion turbine (CT) inlet cooling investigates the instrumentation and methodology options available for testing fogger systems for cooling CT inlet air. Test protocols are presented for the steady state water balance and heat balance measurements. Estimated test uncertainties are presented for the direct measurement of cooling, heat balance, and power curve test methods. In-situ hot wire instrumentation is considered for measuring the carryover. The benefits of computational fluid dynamics (CFD) analysis are illustrated for guidance in the location and in defining the requirements of the instrumentation. Supporting test data for in-situ, heat balance, and power curve tests are included in the report. Test procedures and a method to correct the test results to the guarantee condition are presented. This investigation supports the development of code tests being developed by the ASME PTC 51 Committee.
The Correlation of IR Microturbine Combustion Performance While Burning Diluted Gaseous Fuel Supplied by a Fuel Mixing Facility
Authors: Dolak Eric J. , Armstrong Jeffrey P.
Published: November 2008

Ingersoll-Rand Energy Systems commissioned the construction of a fuel mixing facility to test its commercial microturbines fueled with alternative fuels like those produced by landfills, agricultural digesters, wastewater treatment plants, and petroleum gas well heads. This paper provides an overview of the fuel mixing facility and its capabilities, a discussion of diluted fuel compositions that are typically found in field applications, and a summary of the combustion performance of the IR 250 kW and 70 kW microturbines while operating on diluted fuels (LHV < 34 MJ/m3). The pollutant emission measurements taken with the microturbine burning diluted fuel supplied by the fuel mixing facility are compared with the measured emissions taken from a microturbine operating at a landfill to provide validation of the measurements gathered from the fuel mixing facility. Pollutant emissions are closely tied to not only the magnitude of diluents, but the composition of the diluents as well.
Clad Metal Strips and Foils Engineered for High-Temperature Performance
Authors: Chen L. , Maziasz P. J.
Published: November 2008

In order to increase the engine efficiencies in small size gas turbines and microturbines, recuperators with operating temperatures over 700°C have been developed and evaluated recently. This provides challenges to materials developers and researchers for new solutions in high temperature alloys. The alloys for recuperators should have good performance in high temperature strength, creep resistance and corrosion resistance between 700∼750°C, while their cost should be kept within a reasonable range. Traditionally, clad metals by roll bonding provide both functionality and low cost solutions in demanding corrosion resistance applications and their manufacturing has been well established in large scale production. In this work, cladding technologies, particularly roll bonding, have been reviewed. Two clad metal system approaches, e.g. simple clad metal and clad metal with diffusion alloying, applied for high temperature applications are discussed. The examples of both approaches (SOFC interconnect development, catalytic converter substrate) are presented with test results. Finally, the paper presents a preliminary feasibility study of clad metal for recuperators.
Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycle Technology for Auxiliary Aerospace Power
Authors: Steffen Christopher J. , Freeh Joshua E. , Larosiliere Louis M.
Published: November 2008

A notional 440 kW auxiliary power unit has been developed for 300 passenger commercial transport aircraft in 2015AD. A hybrid engine using solid-oxide fuel cell stacks and a gas turbine bottoming cycle has been considered. Steady-state performance analysis during cruise operation has been presented. Trades between performance efficiency and system mass were conducted with system specific energy as the discriminator. Fuel cell performance was examined with an area specific resistance. The ratio of fuel cell versus turbine power was explored through variable fuel utilization. Area specific resistance, fuel utilization, and mission length had interacting effects upon system specific energy. During cruise operation, the simple cycle fuel cell/gas turbine hybrid was not able to outperform current turbine-driven generators for system specific energy, despite a significant improvement in system efficiency. This was due in part to the increased mass of the hybrid engine, and the increased water flow required for onboard fuel reformation. Two planar, anode-supported cell design concepts were considered. Designs that seek to minimize the metallic interconnect layer mass were seen to have a large effect upon the system mass estimates.
Confinement Effects on the Swirling Flow of a Counter-Rotating Swirl Cup
Authors: Fu Yongqiang , Cai Jun , Jeng San-Mou , Mongia Hukam
Published: November 2008

Gas turbine combustor’s performance, emissions, operability, liner and dome temperature levels and gradients are affected by the degree of confinement expressed indirectly by the dome reference velocity. An experimental investigation was therefore undertaken to characterize the aerodynamic characteristics of non-reacting swirling flow generated by a counter-rotating swirl cup as affected by the test section dimensions. A two-component Laser Doppler Velocimetry (LDV) system was used to measure the mean velocity components and Reynolds stresses of the flowfield generated by the swirl cup installed in 8 square box test sections with width of 3.0, 4.0, 4.1, 4.3, 4.4, 4.5, 5.0, and 6.0 inch, in addition to unconfined flow. Measurements were carried out at fourteen axial distances ranging from 3 to 250 mm downstream of the flare exit, and the radial profiles are obtained through 2 mm intervals. Detailed experimental data are provided to improve mechanistic understanding of the swirl cup generated flowfield as impacted by the ratio of the test section cross-section to the mixer’s effective area. The benchmark quality data are planned for validating the state-of-the-art numerical models in addition more advanced LES approach.
Second Law Analysis of a Novel Combined Cooling and Power Cycle With Water Harvesting
Authors: Khan J. R. , Lear W. E. , Sherif S. A. , Crittenden John F.
Published: November 2008

The first and second laws of thermodynamics were used to analyze a novel cooling and power cycle that combines a semi-closed cycle called the High Pressure Regenerative Turbine Engine (HPRTE) with a vapor absorption refrigeration system (VARS). Waste heat from the recirculated combustion gas of the HPRTE is used to power the absorption refrigeration unit, which cools the high-pressure compressor inlet of the HPRTE to below ambient conditions and also produces excess refrigeration in an amount that depends on ambient conditions. The cycle is modeled using steady-state thermodynamics, with state-of-the-art polytropic efficiencies and pressure drops for the turbo-machinery and heat exchangers, and accurate correlations for the properties of the NH3-water mixture and the combustion products. Exergy analyses were performed for all the components of the cycle to examine the losses and identify critical plant devices considering different operating conditions. Water produced as a product of combustion is intentionally condensed in the evaporator of the VARS, which is designed to provide sufficient cooling for: the inlet air to the high pressure compressor, water extraction and for an external load. The cycle is shown to operate with a thermal efficiency approaching 46% for a turbine inlet temperature of 1400°C while producing about 1.5 kg of water for each kg of fuel (propane) consumed. The thermal efficiency does not take into account the cooling effect produced in the evaporator of VARS. The combined cycle efficiency at the above operating condition was found to be 49%. Low emissions are also possible on liquid fuels and not just on natural gas. It should be noted that the values of efficiencies obtained are for a medium sized engine with conservative values of the design parameters. It is observed that the largest contribution to the total cycle irreversibility comes from the combustor and accounts for 85% of the total exergy loss. The generator of the vapor absorption refrigeration system is the next largest quantity, accounting for about 3.4% of the total exergy loss. The mass of water extracted from the system increases as the value of the low-pressure compressor ratio is increased. However, this rate of increase is more when the compressor ratio is increased from 1.0 to 2.0 and less as the compressor ratio is further increased. Based on these and prior results, which showed that the HPRTE is very compact and has inherently low emissions, it appears that this cycle would be ideally suited for distributed power and vehicle applications, especially ones with associated air conditioning loads.
Evaluation and Characterization of Iron- and Nickel-Based Alloys for Microturbine Recuperators
Authors: Lara-Curzio Edgar , Trejo R. , More K. L. , Maziasz P. J. , Pint B. A.
Published: November 2008

The effects of stress, temperature and time of exposure to microturbine exhaust gases on the mechanical properties and corrosion resistance of alloys HR-120® and 230® was investigated at turbine exhaust temperatures between 620°C and 760°C. It was found that the ultimate tensile strength and ductility of alloy 230® decreased by 30% and 60%, respectively, after 500 hours exposure at 752°C. At the lowest exposure temperature of 679°C the ultimate tensile strength and ductility decreased by 10% and 25%, respectively. The ultimate tensile strength and ductility of HR-120® alloy decreased by 15% and 50%, respectively, after 500 hours exposure at 745°C. At the lowest exposure temperature of 632°C the ultimate tensile strength and ductility decreased by 10% and 23%, respectively. The microstructural changes associated with exposure to microturbine exhaust gases are analyzed and discussed.