bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Effect of Slot Injection, Effusion Array and Dilution Hole on the Cooling Performance of a Real Combustor Liner
Authors: Ceccherini Alberto , Facchini Bruno , Tarchi Lorenzo , Toni Lorenzo , Coutandin Daniele
Published: February 2010

Due to the higher cooling requirements of novel combustor liners a comprehensive understanding of the phenomena concerning the interaction of hot gases with different coolant flows plays a major role in the definition of a well performing liner. An experimental analysis of a real engine cooling scheme was performed on a test article replicating a slot injection and an effusion array with a central large dilution hole. Test section consists of a rectangular cross-section duct and a flat perforated plate with 272 holes arranged in 29 staggered rows (d = 1.65 mm, Sx/d = 7.6, Sy/d = 6, L/d = 5.5, α = 30 deg); a dilution hole (D = 18.75 mm) is located at the 14th row. Both effusion and dilution holes are fed by a channel replicating combustor annulus, that allows to control cold gas side cross-flow parameters. Upstream the first effusion row, a 6.0 mm high slot ensure the protection of the very first region of the liner. Final aim was the measurement of adiabatic effectiveness of the cooling scheme by means of a steady-state Thermochromic Liquid Crystals (TLC) technique, considering the combined effects of slot, effusion and dilution holes. Experiments were carried out imposing three different effusion velocity ratios typical of modern engine working conditions (VReff = 3, 5, 7) and keeping constant slot flow parameters (VRsl = 1.1). CFD RANS calculations were also performed with the aim of better understanding interactions between coolant exiting from the slot and injected by effusion cooling rows. Numerical analysis revealed a large dependency on effusion velocity ratio. An in-house one-dimensional fluid network solver was finally used to compare experimental and numerical results with the ones predicted by correlations and then quantify the possibility of giving predictions. Both CFD and experimental results reveal that slot protection is reduced in the first rows by coolant injected with such high velocity ratios; nevertheless effusion, though in penetration regime, guarantees a significant effectiveness level in the more downstream region. Dilution hole alters the effectiveness growth rate, moreover leading to local protection lowering just after its injection.
Development of a One-Dimensional Dynamic Gas Turbine Secondary Air System Model—Part II: Assembly and Validation of a Complete Network
Authors: Calcagni C. , Gallar L. , Pachidis V.
Published: February 2010

In the first part of this paper the equations and results for the transient models developed for the SAS components in isolation have been thoroughly explained together with the assumptions made and the limitations that arose subsequently. This second part explains the work carried out to couple the individual components into a single network with the aim of assembling a dynamic model for the whole engine air system. To the authors’ knowledge the models published hitherto are only valid for steady or quasi steady state. It is then the case that the differential equations that govern the fluid movement are not time discretised and thus can be solved in a relatively straightforward fashion. Unlike during transients, the flow is not supposed to reach sonic conditions anywhere within the network and most important, flow reversal cannot be accounted for. This study deals with the mathematical apparatus utilised and the difficulties found to integrate the single components into a network to predict the transient operation of the air system. The flow regime — subsonic or supersonic — and its direction have deemed the choice of the appropriate numerical and physical boundary conditions at the components’ interface for each time step particularly important. The integration is successfully validated against a known numerical benchmark — the De Haller test. A parametric analysis is then carried out to assess the effect of the length of the pipes that connect the system cavities on the pressure evolution in a downstream reservoir. Transient flow through connecting pipes is dependent on the fluid inertia and so it takes a certain time for the information to be transported from one end of the duct to the other. As it would be expected, the system with a longer pipe is found to have a longer settling time. Finally, the work concludes with the analysis of the flow evolution in the secondary air system during a shaft failure event. This work is intended to continue to address the limitations imposed by some of the assumptions made for an extended and more accurate applicability of the tool.
Air-Standard Aerothermodynamic Analysis of Gas Turbine Engines With Wave Rotor Combustion
Authors: Nalim Razi , Li Hongwei , Akbari Pezhman
Published: February 2010

The wave rotor combustor can significantly improve gas turbine engine performance by implementing constant-volume combustion. The periodically open and closed combustor complicates thermodynamic analysis, and key cycle parameters depend on complex gas dynamics. In this study, a consistent air-standard aerothermodynamic model with variable specific heat is established. An algebraic model of the dominant gas dynamics estimates fill fraction and internal wave compression for typical port designs, using a relevant flow Mach number to represent wave amplitudes of compression and expansion. Nonlinear equations for thermodynamic state variables are solved numerically by Newton-Raphson iteration. Performance measures and key operating conditions are predicted, and a quasi-one-dimensional computational model is used to evaluate the usefulness of the algebraic model.
Numerical and Experimental Investigation of a Micromix Combustor for a Hydrogen Fuelled µ-Scale Gas Turbine
Authors: Robinson A. E. , Funke H. H.-W. , Wagemakers R. , Grossen J. , Bosschaerts W. , Hendrick P.
Published: February 2010

This last decade has shown an increased interest in the downsizing of gas turbines to micro-scale. Their potential for high energy density makes them extremely attractive for small scale high power units as alternative to traditional unwieldy accumulators or as thrust systems in small robots and unmanned aerial vehicles (UAVs). Beneath great challenges with the rotating parts at this small scale, another crucial item is in fact the combustion chamber needed for a safe and reliable operation. This paper presents a study to an alternative approach in μ-scale hydrogen combustion. The burning principle is based upon the so-called inverse micromix injection. In this non-premixed design, hydrogen fuel is introduced through a porous metal and injected in the axial direction into the combustion chamber. A CFD-model has been implemented to parameterise the different geometrical aspects of the combustion chamber and is set up as a 2D axis-symmetric model to allow for a rapid optimisation of the parameters. The flow calculations are done with a commercial CFD-software. The final optimised geometry showed stable combustion, a well suited temperature profile and acceptable wall temperatures. An overview on the influence of the critical design parameters for the different geometries is presented. Experimental investigations comprise a set of mass flow variations coupled with a variation of the equivalence ratio for each mass flow but always at ambient pressure conditions. With the data obtained by an exhaust gas analysis, a full characterisation concerning combustion efficiency and stability of the burning principle is possible. Combined with the wall temperature measurements, these results lead to a further validation of the CFD model.
Combined Experimental and CFD Study of a HP Blade Multi-Pass Cooling System
Authors: Jackson D. , Ireland P. , Cheong B.
Published: February 2010

Progress in the computing power available for CFD predictions now means that full geometry, 3 dimensional predictions are now routinely used in internal cooling system design. This paper reports recent work at Rolls-Royce which has compared the flow and htc predictions in a modern HP turbine cooling system to experiments. The triple pass cooling system includes film cooling vents and inclined ribs. The high resolution heat transfer experiments show that different cooling performance features are predicted with different levels of fidelity by the CFD. The research also revealed the sensitivity of the prediction to accurate modelling of the film cooling hole discharge coefficients and a detailed comparison of the authors’ computer predictions to data available in the literature is reported. Mixed bulk temperature is frequently used in the determination of heat transfer coefficient from experimental data. The current CFD data is used to compare the mixed bulk temperature to the duct centreline temperature. The latter is measured experimentally and the effect of the difference between mixed bulk and centreline temperature is considered in detail.
Effect of Increasing Pitch-to-Diameter Ratio on the Film Cooling Effectiveness of Shaped and Cylindrical Holes Embedded in Trenches
Authors: Zuniga Humberto A. , Kapat Jayanta S.
Published: February 2010

The continuous push for higher gas turbine inlet temperatures and operating efficiencies has led to increasingly sophisticated film cooling schemes. One such setup—trench cooling—consists of having film cooling holes embedded inside a gap, commonly called a trench. The coolant hits the downstream trench wall which forces it to spread laterally, resulting in more even film coverage downstream. Recent literature has focused on the effect that trenching has on cylindrical cooling holes only. In addition, researchers have limited their findings to a narrow range of pitch-to-diameter ratios (P/D). The current trends in the turbine industry of increasing or maintaining film cooling effectiveness while reducing the amount of coolant used dictate that P/D be increased, meaning less holes per row. In this study, we address both cylindrical and fan-shaped holes embedded in trenches. Tests have been conducted on 8 test plates with one row of cooling holes each varying the pitch-to-diameter ratio from 4 to 12 (12 configurations in total), and the blowing ratios from 0.5 to 2.0. We investigate the effect that P/D has on film cooling effectiveness for both hole geometries and compare them to similarly pitched baseline plates—fan and cylindrical—not in trenches. It is a known fact that increasing the pitch between holes, while maintaining all other conditions constant, decreases the average film effectiveness, however trenching has been shown to significantly increase film coverage. In this study, it has been shown that film cooling effectiveness of a cylindrical configuration can be maintained by the addition of a trench while cutting the number of holes in half. We also explore the behavior of shaped trenched holes, of which little has been said and find that their performance is actually hurt by trenching.
Substrate Damage Modeling for Advanced Turbine System Airfoils
Authors: Karaivanov Ventzislav G. , Siw Sean , Chyu Minking K. , Slaughter William S. , Alvin Mary Anne
Published: February 2010

The Department of Energy (DOE) is developing advanced hydrogen-fired and oxy-fueled turbine technologies that are projected to operate with turbine inlet temperatures (TIT) of 1425°C and 1760°C, respectively. At these temperatures, the airfoil will require not only internal cooling, but also stable thermal barrier coatings (TBCs) in order to achieve extended service operation in these advanced high steam-containing environments. We previously developed a computational methodology, based on three-dimensional finite element analysis (FEA) and damage mechanics, for predicting the evolution of creep in the hydrogen-fired and oxy-fueled airfoils. This methodology has been extended to fatigue damage evolution. Currently, the model allows for the interaction between creep and fatigue damage. Simulation results will be presented that visualize creep and fatigue damage for hydrogen-fired and oxy-fuel airfoils. Additionally, the influence of dynamic changes in the TBC microstructure and phase composition with operational time will be discussed relative to all projected damage mechanisms.
Innovative Design Features of the SGT5-8000H Turbine and Secondary Air System
Authors: Rudolph Ronald , Sunshine Robert , Woodhall Michael , Haendler Michael
Published: February 2010

Siemens Energy began the design of its H-class SGT5-8000H gas turbine in October of 2000. Validation testing of the SGT5-8000H prototype gas turbine began in December of 2007 at E.ON Energie’s Irsching, Germany power plant. The innovative turbine and secondary air system was designed by an international team of engineers, drawing on experience from Siemens and Westinghouse as well as experience from aero engines and academia. At the onset of the design, customers were consulted to identify features and functions they considered important. The result is a design that incorporates proven technologies from the current fleet of Siemens engines as well as numerous advanced technologies to create a simple, robust turbine design with H-class efficiency. The paper describes key features of the secondary air system including extractions, pre-swirlers, sealing systems and multi-use cooling. The SGT5-8000H turbine design has many unique features that promote high efficiency, excellent operability and improved maintainability. The paper describes features such as thermal barrier coatings, hydraulic clearance optimization, fast startup capability and stage 1 component removability via the combustor shell. The design is also being applied to the 60 Hz version of this product.
Multidisciplinary Design Space Characterization of a Prediffuser, Strut, and Frame
Authors: Garrison Loren , Walter Sarah
Published: February 2010

The multidisciplinary exploration and characterization of a design space challenges the boundaries of analysis capability and design process structure for many current industrial applications. In the present study, parallel independent structural and aerodynamic analysis of a prediffuser flow path, strut, and frame was performed in conjunction with design of experiments (DoE) techniques to efficiently characterize the multidisciplinary design space. The key interactions between geometric parameters and the sensitivity factors of each parameter in relation to stress output were calculated. Aerodynamic analysis was performed using full three-dimensional steady-state computational fluid dynamics. Key structural performance, aerodynamic performance, and weight drivers were identified through screening analysis using design of experiments. The use of common geometry definitions and an overlapping parameter set allowed for the multidisciplinary evaluation of parameters such as strut fillet radius and strut chord. In addition, it aided in the identification of trade-offs between structural performance and aerodynamic performance. Further design space characterization with respect to aerodynamic performance was performed through the use of a more detailed multilevel full factorial design of experiment. The sensitivity of the aerodynamic performance metrics to mesh resolution and turbulence models was statistically determined as well as the variation due to the strut design parameters using design of experiments techniques to address the uncertainty and variation due to the numerical analysis. Additional design space characterization and visualization were also achieved through the use of multidimensional response surfaces generated based on latin hypercube DoEs. All three levels of fidelity in DoE analysis (two-level screening, two-level full factorial, and latin hypercube) identified the same primary driver in aerodynamic performance. However, the advanced latin hypercube analysis was necessary to accurately characterize the secondary drivers of aerodynamic performance. Application of the advanced Design of Experiments techniques along with parallel aerodynamic and structural analysis has led to a better understanding of the multidisciplinary design space and helped to facilitate design decisions that impact both aerodynamic and structural performance.
Diagnostic Analysis of Maintenance Data of a Gas Turbine for Driving an Electric Generator
Authors: Loboda Igor , Yepifanov Sergey , Feldshteyn Yakov
Published: February 2010

Monitoring algorithms analyzing measured gas path variables provide invaluable insight into gas turbine operating health. Some useful information about a gas turbine and its measurement system can be obtained from a direct analysis of raw measurements. To draw more comprehensive diagnostic information, deviations are usually calculated as discrepancies between the measured and baseline values of monitored variables. The deviations can serve as good indicators of different engine degradation mechanisms. However, there are many negative factors that tend to mask degradation effects. For a long period of time we have analyzed quality of gas path measurement data and a deviation accuracy problem of a gas turbine power plant driving a natural gas pipeline compressor. Possible error sources were examined and some methods were proposed to improve the accuracy of deviation calculations. This paper looks at maintenance data of another object, the General Electric LM2500 gas turbine used as a drive of an electric generator. The data cover prolonged periods of axial compressor fouling with washings between them, and provide valuable information for a deviation examination. In order to reduce deviation errors, the paper considers different cases of the abnormal functioning of the sensors and baseline model inadequacy and proposes measures to avoid them. As a result of these and previous efforts, the deviations have become good fouling indicators. They are capable to quantify the increase of exhaust gas temperature (EGT) and, consequently, to improve planning axial compressor washings.
Heat Transfer for a Turbine Blade With Non-Axisymmetric Endwall Contouring
Authors: Lynch Stephen P. , Sundaram Narayan , Thole Karen A. , Kohli Atul , Lehane Christopher
Published: February 2010

Complex vortical secondary flows that are present near the endwall of an axial gas turbine blade are responsible for high heat transfer rates and high aerodynamic losses. The application of non-axisymmetric, three-dimensional contouring to the endwall surface has been shown to reduce the strength of the vortical flows and decrease total pressure losses when compared to a flat endwall. The reduction of secondary flow strength with non-axisymmetric contouring might also be expected to reduce endwall heat transfer. In this study, measurements of endwall heat transfer were taken for a low-pressure turbine blade geometry with both flat and three-dimensional contoured endwalls. Endwall oil flow visualization indicated a reduction in the passage vortex strength for the contoured endwall geometry. Heat transfer levels were reduced by 20 percent in regions of high heat transfer with the contoured endwall, as compared to the flat endwall. The heat transfer benefit of the endwall contour was not affected by changes in the cascade Reynolds number.
Sealing Effect on the Performance of Squeeze Film Damper
Authors: Xing Changhu , Braun Minel J. , Li Hongmin
Published: February 2010

Seals used in the squeeze film damper restrict the side leakage of the lubricant, thus providing a measure of additional damping. In this paper, the serrated piston ring and end-plate seals are studied numerically using CFD-ACE+, a commercially available finite volume based algorithm. Research shows that the damping coefficients for the piston ring seal decrease in magnitude with the increase in the number of axial grooves in the circumferential direction until they reach a fairly constant value. However, the pressure distribution and hence the hydrodynamic forces are strongly affected by the number and geometry of the axial grooves. The damping coefficients for the end plate seal increase in magnitude rapidly with the decrease of the seal clearance below the clearance of the damper, but increase slowly when the seal clearance is larger than that of the damper. The direct inertia coefficient increases with the decrease in the seal clearance but the magnitude of cross-coupled inertia coefficients increases with the decrease in the seal clearance, and then falls down towards the values for the infinitely long bearing assumption. Both the damping and inertia coefficients increase with the increase in seal length.
A Comparison of Air-Blast and Flow-Blurring Injectors Using Phase Doppler Particle Analyzer Technique
Authors: Simmons Benjamin M. , Panchasara Heena V. , Agrawal Ajay K.
Published: February 2010

Recent research on biofuels for power generation has typically focused on biodiesel because the biodiesel feedstrock, e.g., vegetable oil, poses significant combustion problems related to poor atomization. Existing injectors cannot effectively atomize high viscosity fuels such as vegetable oil. However, a new, novel flow-blurring (FB) injector concept has shown promise in overcoming the atomization problems. In this study, a FB injector is compared to a commercial air-blast (AB) injector operated with water at ambient conditions of temperature and pressure. Laser sheet visualization and Phase Doppler Particle Analyzer (PDPA) systems are used to obtain the spray characteristics for a range of air to liquid (ALR) ratios. Results show significant difference in distributions of Sauter Mean Diameters (SMDs), and mean and root-mean square axial velocity for the two injectors operated at a fixed ALR. In comparison to the AB injector, the FB injector produced spray with smaller SMDs, a smaller SMD range over the spray volume, higher RMS and mean axial velocities in the center region, and a compact spray with spray angle nearly independent of ALR. Results show that the FB injector is an effective way of atomizing liquids at relatively low ALRs compared to a traditional AB injector, without the additional pressure drop penalty.
Experimental and Computational Study of Heat/Mass Transfer and Flow Structure for Four Dimple Shapes in a Square Internal Passage
Authors: Zhou Fuguo , Acharya Sumanta
Published: February 2010

Mass/heat transfer measurements are made using the naphthalene sublimation method in a square internal passage where one wall has a single dimple. Four types of dimple shapes are studied: square, triangular, circular and teardrop. Sherwood numbers are obtained both inside and around the dimples. Measurements are made at a Reynolds number of 21,000. In addition, computations are performed for the same dimple geometries, and with the same flow conditions as in the experiments. Flow patterns for the four dimples are identified, and heat transfer distributions for each dimple are obtained. Computational results are compared with the experimental data and show satisfactory agreement. Both experimental and numerical results suggest that the teardrop dimple has the highest heat /mass transfer among the four dimple shapes studied.
Development of Ultra-Low Emission Liquid Fuel-Fired Microturbine Engines for Vehicular Heavy Duty Applications
Authors: Chen Junhua , Mitchell Mark G. , Nourse John G.
Published: February 2010

Worldwide regulations currently set very stringent emissions standards for new on-road heavy-duty diesel engines (HDDE’s). For example, the United States Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) require 2010 and subsequent HDDE and vehicles to emit less than 0.2 g/bhp-hr (0.27 g/kW-hr) NOx and 5.0 g/bhp-hr (6.7 g/kW-hr) CO in addition to other strictly regulated pollutants. Diesel or biodiesel fired Microturbine engines are in use in hybrid electric vehicular (HEV) urban bus applications because of their extremely low emissions. In Capstone’s model years 2001 through 2003, liquid fueled gas turbines were certified by CARB for on-road heavy duty engine use, including urban bus applications. The engines achieved a low emission level of 0.7 g/hp-hr (0.94 g/kW-hr) NOx, 0.2 g/hp-hr (0.27 g/kW-hr) CO and 0.01 g/hp-hr (0.013 g/kW-hr) PM, which met emissions compliance levels for EPA and CARB regulations until 2010. To meet the upcoming 2010 EPA and CARB HDDE regulations, continuous research and development efforts have been taken at Capstone Turbine Corporation for its C30 family engines to further reduce the criteria pollutant emissions. Pollutant emissions were measured and analyzed for a Capstone C30 engine using ultra low sulfur diesel (ULSD) and five other opportunity fuels to obtain their actual cycle emissions for a typical New York City M60 route. By injector modification alone, the C30 engine was able to achieve 62% reduction in NOx emission. Additionally, an adjustment of turbine exit temperature was able to further reduce NOx. It was predicted that the liquid-fueled C30 engines would be able to demonstrate the compliance to the 2010 EPA/CARB new ultra-low emission standards.
Modeling of Flame Blowout and Emissions in Vitiated Combustion of Biofuels
Authors: Singh Bhupinder , Lear William E.
Published: February 2010

The widening gap between the demand and supply of fossil fuels has catalyzed the exploration of alternative sources of energy. Interest in the Power, Water Extraction and Refrigeration (PoWER) cycle, proposed by the University of Florida, as well as the desirability of using biofuels in distributed generation systems, has motivated the exploration of biofuel vitiated combustion. In earlier research efforts on the PoWER engine, lower emissions have been demonstrated by using conventional diesel fuels, achieved through high levels of exhaust gas recirculation (EGR) in semiclosed (SC) mode of operation, inherent in the PoWER cycle. In this work, combustion performance of biofuels has been investigated through modeling of chemical kinetics of ethanol, dimethyl ether (DME) and biodiesel surrogate methyl butanoate (MB), and comparison was made against conventional diesel fuel that was modeled using surrogate fuel n-heptane. The combustion performance was compared over a range of equivalence ratios and EGR levels. The simulations were performed using a constant-pressure continuously stirred tank reactor (CSTR) model developed using the Camera combustion code, implemented in C++. Results have been presented showing comparative trends in emissions, stability and combustion efficiency.
A Method for Identifying and Visualizing Foreign Particle Motion Using Time Resolved Particle Tracking Velocimetry
Authors: Cardwell N. D. , Vlachos P. P. , Thole K. A.
Published: February 2010

Gas turbines for aircraft are designed for operation with a clean inlet air flow. This ideal operational condition is often violated during take-off and landing, where the probability of particle ingestion is high with sand and dirt being the most commonly observed foreign particles. Current research on particle ingestion has identified several mechanisms that contribute to performance degradation in the turbine: erosion of internal and external surfaces; and flow blockages of film-cooling holes and internal cooling passages. The focus of the study given in this paper is to present a method that identifies the motion of foreign particles within an internal ribbed passage. The method uses a high-resolution, flowfield interrogation method known as Time-Resolved Digital Particle Image Velocimetry (TRDPIV). Observations from the two-phase flows showed that particle collisions occurred more frequently on the upstream surface of the ribs, especially in the inlet region. Results from these collisions included substantial particle breakup and a particle rebounding phenomenon between the upper and lower walls. Comparisons are made to LES predicted particle trajectories indicating some agreement, but also phenomena that are not predicted due to the inherent assumption of the modeling.
The Influence of Rotating Speed on Film Cooling Characteristics on GE-E3 Blade Tip With Different Tip Configurations
Authors: Zhang D. H. , Zeng M. , Wang Q. W.
Published: February 2010

The film cooling phenomenon of flat tip (with or without a trench) and squealer tip on GE-E3 blade in rotating state was numerically studied. The effect of tip configuration, rotating speed and blowing ratio on the blade tip flow and cooling performance was revealed. It was found that the squealer tip and the flat tip with trenched hole have comparability in configuration: both have a cavity at the end of the film hole. So the coolant momentum and the tip leakage flow velocity in the cavity are decreased, which contributes to the improvement of the cooling effect. Because of the bigger cavity of the squealer tip than that of the flat tip with trenched hole, the cooling air and the leakage flow mix adequately in the cavity, the squealer tip can get the highest cooling effectiveness and the lowest heat transfer coefficient value both in stationary and rotating state, and the flat tip with trenched hole follows. With the increase of rotating speed, for all the three configurations, the area-averaged cooling effectiveness decreases and the area-averaged heat transfer coefficient increases. At the same time, the tip leakage flow entraps the cooling air moving toward the leading edge. And with the increase of the blowing ratio, for all the configurations, the area-averaged cooling effectiveness increases while the area-averaged heat transfer coefficients decreases.
Design Overview of a Three-Kilowatt Recuperated Ceramic Turboshaft Engine
Authors: Vick Michael J. , Heyes Andrew , Pullen Keith
Published: February 2010

A three-kilowatt turboshaft engine with a ceramic recuperator and turbine has been designed for small unmanned air vehicle (UAV) propulsion and portable power generation. Compared with internal combustion (IC) engines, gas turbines offer superior reliability, engine life, noise and vibration characteristics, and compatibility with military fuels. However, the efficiency of miniature gas turbines must be improved substantially, without severely compromising weight and cost, if they are to compete effectively with small IC engines for long-endurance UAV propulsion. This paper presents a design overview and supporting analytical results for an engine that could meet this goal. The system architecture was chosen to accommodate the limitations of mature, cost-effective ceramic materials: silicon nitride for the turbine rotors, and toughened mullite for the heat exchanger and turbine stators. An engine with a cycle pressure ratio below 2:1, a multistage turbine, and a highly effective recuperator is shown to have numerous advantages in this context. A key benefit is a very low water-vapor-induced surface recession rate for silicon nitride, due to an extremely low partial pressure of water in the combustion products. Others include reduced sensitivity to internal flaws, creep, and foreign object damage; an output shaft speed low enough for grease-lubricated bearings; and the potential viability of a novel premixed heat-recirculating combustor.
Towards Prediction and Control of Large Scale Turbulent Structure Supersonic Jet Noise
Authors: Schlinker Robert H. , Reba Ramons A. , Simonich John C. , Colonius Tim , Gudmundsson Kristjan , Ladeinde Foluso
Published: February 2010

In this paper, we report on progress towards developing physics-based models of sound generation by large-scale turbulent structures in supersonic jet shear layers generally accepted to be the source of aft-angle noise. Aside from obtaining better engineering prediction schemes, the development and optimization of long term jet noise reduction strategies based on controlling instability wave generated large-scale turbulence structures in the shear layer can be more successful if based on predictive flow-noise models, rather than on build and test approaches alone. Such models, if successful, may also provide a path by which laboratory scale demonstrations can be more reliably translated to engine scale. Results show that the noise radiated by large-scale structures in turbulent jet shear layers may be modeled using a RANS based PSE method and projected to the far-field using a Kirchhoff surface approach. A key enabler in this procedure is the development of near-field microphone arrays capable of providing the pressure statistics needed to validate the instability wave models. Our framework provides, for the first time, a deterministic model that will allow understanding and predicting noise radiated by large-scale turbulence.
Experimental and Numerical Study of the Thermal Performance of a Film Cooled Turbine Platform
Authors: Charbonnier D. , Ott P. , Jonsson M. , Cottier F. , Ko¨bke Th.
Published: February 2010

Detailed surface measurements of the thermal performance of a film cooling system have been performed on the endwall of a nozzle guide vane (NGV) mounted in a linear cascade facility at EPFL. An external cooling scheme including several rows of fan-shaped and cylindrical cooling holes has been designed. By testing different cooling flow rates at a NGV exit Reynolds number of 1.7E+06 and Mach number of 0.88, detailed aerodynamic and heat transfer values were obtained destined to assess the design tools for film cooled platforms. The surface static pressure distribution and the film cooling effectiveness on the endwall surface have been experimentally determined. The measurements were obtained applying the pressure sensitive paint technique measuring the coolant gas concentration. An engine representative density ratio between the coolant and the external hot gas flow was achieved by the injection of CO2. The working conditions of the test case similar to realistic engine conditions allow for the validation of in-house CFD codes and the investigation of the reliability of modern commercial tools in such a complex cooling system. The numerical campaign has been performed on the same numerical grid, using the commercial codes FLUENT and CFX, used by EPFL and MTU respectively. A detailed analysis of the grid effects on the obtained results has been previously realised as well as the study of the influence of the modelling approximations. Three cooling mass flows have been simulated and the performance parameters of the film cooling system have been compared to the experimentally obtained data. Special emphasis has been put on the jet penetration effects and on the interaction of secondary flows with the coolant flow. The experimental and numerical efforts were part of the EU funded research project TATEF2 (Turbine Aero-Thermal External Flows 2).
Design of a Novel Quad-Generation Distributed Energy Demonstration Plant
Authors: Tiffany D. R. , Lear W. E. , Harris M. A. , Crittenden J. F.
Published: February 2010

The power water extraction and refrigeration (PoWER) — a derivative of the high pressure regenerative turbine engine (HPRTE) — has been investigated as part of the distributed energy concept. The ability of the cycle to hold efficiency nearly constant over a wide range of loads and ambient condition is a strong advantage over other concepts. Additional benefits in water extraction and auxiliary refrigeration also pose attractive possibilities. The semi-closed cycle allows for operation in the flameless combustion regime, which can yield substantial emissions reductions as well as fuel flexibility. As part of a continuing effort to illustrate this cycle’s potential, an on-grid demonstration plant is being constructed. The project is part of a collaboration among the University of Florida, Florida Turbine Technology, Energy Concepts, Inc., and Progress Energy. This new pilot plant, while not demonstrating the high efficiency of fully optimized product, is intended to validate cycle analysis codes, produce air conditioning and fresh water, and allow startup and part power operation to be assessed. Quantifying the transient performance, physics-bases multivariate control, and fundamental investigation into the flameless combustion regime — especially with bio-derived fuels — are also goals of the project. This paper describes the modeling effort for the design of the demonstration plant. The modeling proceeded in parallel with the plant development, and was used for hardware selection, integration of the various subsystems, as well as to aid in initial testing of the plant. The model has full capability to predict plant performance over a wide range of steady state conditions. The effect of different fuels and ambient can be considered. Once validated by actual performance data, this code can be used for further prediction, as well as to explore future plant modifications.
Development and Testing of Harsh Environment, Wireless Sensor Systems for Industrial Gas Turbines
Authors: Mitchell David , Kulkarni Anand , Lostetter Alex , Schupbach Marcelo , Fraley John , Waits Rod
Published: February 2010

The potential for savings provided to worldwide operators of industrial gas turbines, by transitioning from the current standard of interval-based maintenance to condition-based maintenance may be in the hundreds of millions of dollars. In addition, the operational flexibility that may be obtained by knowing the historical and current condition of life-limiting components will enable more efficient use of industrial gas turbine resources, with less risk of unplanned outages as a result of off-parameter operations. To date, it has been impossible to apply true condition-based maintenance to industrial gas turbines because the extremely harsh operating conditions in the heart of a gas turbine preclude using the necessary advanced sensor systems to monitor the machine’s condition continuously. Siemens, Rove Technical Services, and Arkansas Power Electronics International are working together to develop a potentially industry-changing technology to build smart, self-aware engine components that incorporate embedded, harsh-environment-capable sensors and high temperature capable wireless telemetry systems for continuously monitoring component condition in the hot gas path turbine sections. The approach involves embedding sensors on complex shapes, such as turbine blades, embedding wireless telemetry systems in regions with temperatures that preclude the use of conventional silicon-based electronics, and successfully transmitting the sensor information from an environment very hostile to wireless signals. The results presented will include those from advanced, harsh environment sensor and wireless telemetry component development activities. In addition, results from laboratory and high temperature rig and spin testing will be discussed.
Effect of Face-Area Ratio on Heat-Exchanger Pressure Drops, Size and Weight
Authors: Wilson David Gordon
Published: February 2010

Designers of heat exchangers of all types normally have several degrees of freedom even while meeting the specified effectiveness exactly. One freedom is that of choosing the face-area ratios for the two (or more) fluids. A principal reason for choosing face-area ratio is to arrive at desired pressure drops for the fluids. The lowest pressure drop is not always beneficial: a low pressure drop can produce highly non-uniform flow that would degrade heat-exchanger performance. Obviously a high pressure drop penalizes system performance directly. In this paper it is shown that choosing face-area ratio is a good tool up to a point, one at which penalties in the form of increased size and cost of the overall heat exchanger begin to outweigh the benefits. This paper reports studies on the effects of choosing face-area ratios on rotary regenerative heat exchangers, but most results are applicable to fixed-surface recuperative heat exchangers also. However, one significant difference between the two types is that gas-turbine regenerators have short flow lengths, the thickness of the disk or drum. A short flow length is a virtue, because it reduces the regenerator disk volume and mass. But the disk thickness must not be allowed to be reduced to the point where there is substantial “short-circuit” thermal conduction between the hot and cold faces of a regenerator. These and other aspects of heat-exchanger design are explored in general and by means of examples, and design guidelines are suggested.
Residual Life Assessment and Life Cycle Management of Design Life Expired Discs
Authors: Koul Ashok , Tiku Ajay , Khullar Karan , Zhao Jun
Published: February 2010

The results of a prognostics case study on GE Frame 5001P first stage turbine disc are presented in this paper. Currently used and promoted practices for metallurgical analysis such as hardness testing and replica based microstructural assessment and inspection of rotors for dimensional checks and cracks are not sufficient to ensure safety and reliability of the engine. The uncertainly of all engine variables including operational environment must be considered prior to returning the engine to service. It is required to accurately predict the temperature profile of the discs that can have serious consequences on the residual life assessment of the fracture prone rotors. The safe inspection interval (SII) determination of the design life expired engines and defining non-destructive inspection (NDI) sensitivity requirements for continued safe operation of the engine are equally important.
Re-Sizing of a Natural Gas Fired Two-Shaft Gas Turbine for Low Calorific Gas Operation
Authors: Eriksson Pontus , Jonshagen Klas , Klingmann Jens , Genrup Magnus
Published: February 2010

Gas turbine systems are predominantly designed to be fuelled with gaseous fuels within a limited Wobbe index range (typically HHV = 45–55 MJ/Nm3 or 1200–1480 Btu/scf). When low calorific fuel gases are fired, the engine will be forced to operate outside its design envelope. The added mass flow will typically raise the cycle pressure ratio and in two-shaft designs also raise the gas generator shaft speed. In this study, the response of a natural gas fired simple cycle two-shaft gas turbine operating at full firing temperature is investigated. A model based on the Volvo Aero Corp. VT4400 gas turbine (originally Dresser Rand DR990) characterized by one compressor and two expander maps is considered. The free turbine is operated at fixed physical speed. Different amounts of N2 or CO2 are added to the fuel path. These two inerts are typically found in large quantities in medium and low calorific fuels. The fuels lower heating value is thus gradually changed from 50 MJ/kg (21.5 kBtu/lb) to 5MJ/kg (2.15 kBtu/lb). Emphasis has been put on predicting the compressor behavior in different resizing scenarios. The full ‘firing temperature’ operating point in the compressor map is tracked as the compressor size is reduced up to 7.5%, high pressure turbine size is increased up to 20%, low pressure turbine size is changed ±7.5% or up to 10% of steam (c.f. design point compressor air mass flow) is injected between the turbines. Different re-matching schemes are discussed where one turbomachinery component size is fixed and the two other component sizes are changed such that the compressor design point is restored. Finally a re-optimized turbine flow path is computed in a fixed compressor size scenario. Results are, as far as possible, given as non-dimensional parameter groups for easy comparison with other machines.
A Brief History of the T4 Radiation Law
Authors: Crepeau John
Published: February 2010

Since the 1700s, natural philosophers understood that heat exchange between two bodies was not precisely linearly dependent on the temperature difference, and that at high temperatures the discrepancy became greater. Over the years, many models were developed with varying degrees of success. The lack of success was due to the difficulty obtaining accurate experimental data, and a lack of knowledge of the fundamental mechanisms underlying radiation heat exchange. Josef Stefan, of the University of Vienna, compiled data taken by a number of researchers who used various methods to obtain their data, and in 1879 proposed a unique relation to model the dependence of radiative heat exchange on the temperature: the T4 law. Stefan’s model was met with some skepticism and was not widely accepted by his colleagues. His former student, Ludwig Boltzmann, who by then had taken a position at the University of Graz in Austria, felt that there was some truth to the empirical model proposed by his mentor. Boltzmann proceeded to show in 1884, treating electromagnetic radiation as the working fluid in a Carnot cycle, that in fact the T4 law was correct. By the time that Boltzmann published his thermodynamic derivation of the radiation law, physicists became interested in the fundamental nature of electromagnetic radiation and its relation to energy, specifically determining the frequency distribution of blackbody radiation. Among this group of investigators was Wilhelm Wien, working at Physikalisch-Technische Reichsanstalt in Charlottenburg, Berlin. He proposed a relation stating that the wavelength at which the maximum amount of radiation was emitted occurred when the product of the wavelength and the temperature was equal to a constant. This became known as Wien’s Displacement Law, which he deduced this by imagining an expanding and contracting cavity, filled with radiation. Later, he combined his Displacement Law with the T4 law to give a blackbody spectrum which was accurate over some ranges, but diverged in the far infrared. Max Planck, at the University of Berlin, built on Wien’s model but, as Planck himself stated, “the energy of radiation is distributed in a completely irregular manner among the individual partial vibrations...” This “irregular” or discrete treatment of the radiation became the basis for quantum mechanics and a revolution in physics. This paper will present brief biographies of the four pillars of the T4 radiation law, Stefan, Boltzmann, Wien and Planck, and outline the methodologies used to obtain their results.
Effect of the Capillary Property of Porous Media on the Water Transport Characteristics in a Passive Liquid-Feed DMFC
Authors: Xu Chao , Faghri Amir
Published: February 2010

The porous diffusion medium (DM) used in fuel cells has a complex heterogeneous structure in which both hydrophilic and hydrophobic pores coexist. The capillary flow in such a mixed-wet DM is mainly controlled by the capillary pressure and saturation relation (CPSR). In order to investigate the water transport characteristics in a passive DMFC, taking into account the coexistence of the hydrophilic and hydrophobic pores in the DM, we presented the mechanisms of capillary flow in the mixed-wet DM and provided a comprehensive evaluation of the CPSRs used in various existing fuel cell studies. Then, based on a two-dimensional two-phase non-isothermal model for the passive DMFC, we also investigated the liquid transport phenomena through the mixed-wet DM by employing an experimentally measured mixed-wet CPSR. Moreover, we compared the water transport predicted by the mixed-wet CPSR and the uniform-wet Leverett CPSR for better understanding of the liquid water transport in passive DMFCs. The results show that water transport in the passive DMFC depends greatly on the CPSR of the DM, which demonstrates an urgent need for the accurate CPSRs of the DM used in fuel cells. It is also shown that the dependence of water transport on the CPSRs can be significantly influenced by the use of a hydrophobic air filter layer at the cathode.