bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Vane Surface Film Cooling Effectiveness Using Compressible Navier-Stokes Procedure and k-ε Turbulence Model With Wall Function
Authors: Fukuyama Yoshitaka , Otomo Fumio , Sato Minoru , Kobayashi Yuichi , Matsuzaki Hiroyuki
Published: February 2015

A numerical prediction has been performed on the film cooling effectiveness and the total pressure loss of the actual turbine vane geometry. The Navier-Stokes code used in this study is an implicit, cell-centered, finite volume code with k-ε turbulence models. The convection term was stabilized by the variable order up-winding scheme. The film cooling injection has been simulated by adding the prescribed flux terms at the vane surface.

The k and ε near wall distribution functions were developed based on the experimental and the DNS results in the literature. The wall functions for k and ε can be used with the selected low Reynolds number version of k-ε turbulence model irrespective of the distance between the wall and the first grid point. This combination would result in lower computational costs, since, near wall grid number can be reduced significantly.

Based on the study, the Navier-Stokes predictions were performed on the actual turbine vane geometry. Also, the comparisons were made with the experimental total pressure loss distribution behind the vane row and the mid-span film-cooling effectiveness distribution for single and double row injection cases.
The Development of Life Prediction Techniques for Structural Ceramics
Authors: Khandelwal P. K. , Provenzano N. J. , Schneider W. E.
Published: February 2015

One of the major challenges involved in the use of ceramic materials in advanced vehicular heat engines is ensuring adequate strength and durability. This Department of Energy supported activity has developed methodologies to predict the structural behavior of ceramic components. The effort involved the characterization of injection molded and hot isostatic pressed PY6 silicon nitride and the development of analytical life prediction techniques. Three failure modes are addressed: fast fracture, slow crack growth, and creep rupture. The technique deals with surface as well as internal component failures. The life prediction methodologies for fast fracture and slow crack growth have been verified using two types of confirmatory specimens: (1) flat circular disks subjected to bending stresses and (2) high speed rotating spin disks. Correlation was achieved for a variety of test conditions and failure mechanisms. The predictions associated with surface failures proved to be optimistic requiring reevaluation of the components initial fast fracture strength. Correlation was achieved for the spin disks that failed in fast fracture from internal flaws. Time dependent elevated temperature spin disk failures were also successfully predicted.
Reliability Analysis of Uniaxially Ground Brittle Materials
Authors: Salem Jonathan A. , Nemeth Noel N. , Powers Lynn M. , Choi Sung R.
Published: February 2015

The fast fracture strength distribution of uniaxially ground, alpha silicon carbide was investigated as a function of grinding angle relative to the principal stress direction in flexure. Both as-ground and ground/annealed surfaces were investigated. The resulting flexural strength distributions were used to verify reliability models and predict the strength distribution of larger plate specimens tested in biaxial flexure. Complete fractography was done on the specimens. Failures occurred from agglomerates, machining cracks, or hybrid flaws that consisted of a machining crack located at a processing agglomerate. Annealing eliminated failures due to machining damage. Reliability analyses were performed using two and three parameter Weibull and Batdorf methodologies. The Weibull size effect was demonstrated for machining flaws. Mixed mode reliability models reasonably predicted the strength distributions of uniaxial flexure and biaxial plate specimens.
The Influence of Neighboring Blade Rows on the Unsteady Aerodynamic Response of Cascades
Authors: Hall Kenneth C. , Silkowski Peter D.
Published: February 2015

In this paper, we present an analysis of the unsteady aerodynamic response of cascades due to incident gusts (the forced response problem) or blade vibration (the flutter problem) when the cascade is part of a multistage fan, compressor, or turbine. Most current unsteady aerodynamic models assume the cascade to be isolated in an infinitely long duct. This assumption, however, neglects the potentially important influence of neighboring blade rows. We present an elegant and computationally efficient method to model these neighboring blade row effects. In the present method, we model the unsteady aerodynamic response due to so-called spinning modes (pressure and vorticity waves), with each mode corresponding to a different circumferential wave number and frequency. Then, for each mode, we compute the reflection and transmission coefficients for each blade row. These coefficients can be obtained from any of the currently available unsteady linearized aerodynamic models of isolated cascades. A set of linear equations is then constructed that couples together the various spinning modes, and the linear equations are solved via LU decomposition. Numerical results are presented for both the gust response and blade vibration problems. To validate our model, we compare our results to other analytical models, and to a multistage vortex lattice model. We show that the effect of neighboring blade rows on the aerodynamic damping of vibrating cascades is significant, but nevertheless can be modeled with a small number of modes.
Measurements of Heat Transfer Coefficients and Friction Factors in Rib-Roughened Channels Simulating Leading-Edge Cavities of a Modern Turbine Blade
Authors: Taslim M. E. , Li T. , Spring S. D.
Published: February 2015

Leading edge cooling cavities in modern gas turbine blades play an important role in maintaining the leading edge temperature at levels consistent with airfoil design life. These cavities often have a complex cross-sectional shape to be compatible with the external contour of the blade at the leading edge. A survey of many existing geometries show that, for analytical as well as experimental analyses, such cavities can be simplified in shape by a four-sided polygon with one curved side similar to the leading edge curvature, a rectangle with one semi-circular side (often the smaller side) or a trapezoid, the smaller base of which is replaced by a semicircle. Furthermore, to enhance the heat transfer coefficient in these cavities, they are mostly roughened on three sides with ribs of different geometries. Experimental data on friction factors and heat transfer coefficients in such cavities are rare if not nonexistent. A liquid crystal technique was used in this experimental investigation to measure heat transfer coefficients in six test sections representing the leading-edge cooling cavities. Straight as well as tapered ribs were configured on the two opposite sidewalls in a staggered arrangement with angles of attack to the mainstream flow, α, of 60° and 90°. The ribs on the curved surface were of constant cross section with an angle of attack 90° to the flow. Heat transfer measurements were performed on the straight sidewalls as well as on the round surface adjacent to the blade leading edge. Effects such as rib angle of attack to the mainstream flow and constant versus tapered rib cross-sectional areas were also investigated. Nusselt numbers, friction factors and thermal performances are reported for nine rib geometries in six test sections.
On–Engine Evaluation of Emissions Characteristics of a Variable Geometry Lean–Premixed Combustor
Authors: Yamada H. , Shimodaira K. , Hayashi S.
Published: February 2015

The design and on–engine testing of a lean–premixed, low–NOx combustor for a simple cycle, single shaft, 250–kW gas turbine engine of a pressure ratio of eight are described. A variable geometry system composed of butterfly air valves was used to control the combustor air split between combustion and dilution. Fuel was staged to a direct–injection pilot burner and a lean–premixed main burner fitted to the combustor liner. The NOx emissions with natural gas fueling were found to be less than 20 ppm (at 15% O2) at and near full load conditions with combustion efficiencies greater than 99.8%. Emissions data from early high–pressure rig tests of the combustor hardware are also presented.
Jet Fuel Deposition and Oxidation: Dilution, Materials, Oxygen, and Temperature Effects
Authors: Zabarnick Steven , Zelesnik Paula , Grinstead Rebecca R.
Published: February 2015

The quartz crystal microbalance (QCM) and pressure measurements are used for determination of jet fuel thermal stability in a batch reactor. The QCM is able to monitor extremely small amounts of deposition in situ, while the pressure measurements provide qualitative data on the oxidation process. The dependence of the deposition amount was monitored as a function of the oxygen availability for two fuels. Also, the effect of QCM electrode materials was investigated. Deposition and oxidation were compared for the following electrode materials: gold, aluminum, silver, and platinum. We also studied the effect of dilution on oxidation and deposition. Jet fuel was diluted with increasing amounts of hydrocarbon solvent. It was observed that this dilution procedure can help characterize a fuel’s effective antioxidant concentration. Fuel dilution is also shown to be a good technique for improving thermal stability characteristics of poor fuels. Additionally we have studied the temperature effect on deposition for two fuels over the range 140 to 180 C.
Development of a Small Mixed-Flow Turbine for Automotive Turbochargers
Authors: Minegishi Hiroaki , Matsushita Hiromi , Sakakida Masaru , Koike Takaaki
Published: February 2015

In recent years, turbocharging technologies for passenger cars have progressed significantly. However, “Turbo Lag” is still one of the most important problems in turbocharging technologies.

In order to improve response to acceleration, it is effective to reduce the polar moment of inertia of rotating parts. The turbine rotor designed with small diameter, light weight and high specific-speed contributes toward reducing inertia moment of the rotating parts. The further request for the smaller moment of inertia for passenger car applications made it difficult to satisfy the request with a conventional radial turbine rotor. This is why we developed a mixed-flow turbine rotor.

This paper explains the computer analysis we carried out and experimental test data of the mixed-flow turbine for passenger car applications.
Optimum Peak Cycle Pressure for the Intercooled-Supercharged Gas Turbine Engine
Authors: Wang Lin-Shu , Pan Lili
Published: February 2015

Performance (thermal efficiency and mass specific power) of a simple-cycle gas turbine increases monotonically with peak cycle temperatures, for a given peak cycle temperature, the performance also depends on cycle pressure ratio or peak cycle pressure: maximum performance (both mass specific power and thermal efficiency near their maximum values) is achieved in a narrow range of optimum peak cycle pressures.

A recently proposed intercooled-supercharged cycle gas turbine differs from the conventional intercooled cycle gas turbine in their intercooler placement. This paper studies the performance of the proposed cycle based on a reformulated intercooling-supercharging optimization procedure. The intercooler placement is defined by a new parameter, the intercooling supercharging parameter. In terms of the intercooling supercharging parameter and the peak cycle pressure, a map of performance curves (efficiency versus specific power) is constructed, which discloses a higher performance zone for the proposed cycle. This performance zone is defined by optimal intercooler placement and peak cycle pressures that are considerably higher than the simple-cycle’s optimum peak cycle pressures. At these higher pressures, the intercooled-supercharged-cycle gas turbine can achieve a new level of performance: a 20% to 30% improvement over the simple cycle in thermal efficiency and mass specific power.
Semi–Empirical Correlation of NOx Emissions From Combustion Turbines With Water/Steam Injection
Authors: Newburry Donald M. , Mellor Arthur M.
Published: February 2015

Inert (water or steam) injection is commonly used to reduce NOx emissions in stationary gas turbine combustors, both lean premixed when oil–fired and conventional. Thus, having an accurate phenomenological model to predict these reductions could be useful in both design and implementation for low emissions. In this work, the semi–empirical characteristic time model (CTM), which has been validated for thermal NOx emissions from conventional, diffusion flame combustors, is modified to account for inert injection effects. Measured NOx data from two heavy–duty, utility combustion turbines operating on natural gas and fuel oil #2, both dry and with water or steam injection, are correlated.

Inert injection is modeled as thermal, and two limiting cases are proposed which successfully bound the measured data. An empirically selected effective inert injection flame temperature was substituted for the stoichiometric flame temperature used to estimate the thermal NO formation rate in the CTM. This procedure correlated all of the measured data from both combustors for both fuels with a standard deviation of 1.02 g NO2/kg fuel. The high standard deviation results from systematic trends in the dry data for one combustor which propagate through the lower NOx values of the inert injection data. Removing these trends empirically improves the combined correlation to a standard deviation of 0.28 g/kg (approximately 3.2 ppmvd at 15% O2).
Semi–Empirical Predictions and Correlations of NOx Emissions From Utility Combustion Turbines
Authors: Newburry Donald M. , Mellor Arthur M.
Published: February 2015

Semi–empirical equations model the dominant subprocesses involved in pollutant emissions by assigning specific times to the fuel evaporation, chemistry, and turbulent mixing. They then employ linear ratios of these times with model constants established by correlating data from combustors with different geometries, inlet conditions, fuels, and fuel injectors to make a priori predictions.

In this work, thermal NOx emissions from two heavy–duty, dual fuel (natural gas and fuel oil #2) diffusion flame combustors designated A and B operating without inert injection are first predicted, and then correlated using three existing semi–empirical approaches termed the Lefebvre (AHL) model, the Rizk–Mongia (RM) model, and the characteristic time model (CTM). Heterogeneous effects were found to be significant, as fuel droplet evaporation times were required to align the natural gas and fuel oil data. Only the RM model and CTM were employed to study this phenomenon.

The CTM achieved the best overall prediction and correlation, as the data from both combustors fell within one standard deviation of the predicted line. The AHL and RM models were not able to account for the geometries of the two combustors. For Combustor A the CTM parameter correlated the data in a highly linear manner, as expected, but for Combustor B there was significant curvature. Using the CTM this was shown to be a residence time effect.
Local Measurements in a Three Dimensional Jet-Stabilized Model Combustor
Authors: Bauer H. J. , Eigenmann L. , Scherrer B. , Wittig S.
Published: February 2015

Measurements of velocity, temperature and species concentration in a three dimensional jet-stabilized combustor are presented. The modular design of the combustor permits the use of either gaseous or liquid fuels. For the investigations presented here, fuel oil has been chosen which is atomized by an air-blast atomizer. Access to the reacting flow field for probes as well as for non intrusive optical measurement techniques is provided by several windows along the combustor axis.

Velocity measurements in the mixing zone and even in the primary zone of the combustor are performed by means of a two-component Laser Doppler Velocimeter (LDA). Platinum rhodium/platinum thermocouples (PtRh/Pt) specially designed for reduced internal heat losses are used for the investigation of the temperature field. A cranked, water cooled probe is employed in order to detect local species concentrations.

The experimental results reveal detailed information about the characteristics of the reacting flow field. The interaction of fuel atomization and flame stabilization in the primary zone is illustrated by a direct comparison with experimental data of the gaseous fuel case investigated earlier [ 1 ]. The results gained here serve as an excellent database to verify numerical models for the description of liquid spray combustion.
Injection-Molded and Isopressed α-SiC Components for Stationary Gas Turbine Applications
Authors: Ohnsorg R. W. , Lau S. K. , Ten Eyck M. O. , White D. A.
Published: February 2015

Sintered α-SiC (HEXOLOY®1 SA) injection-molded buttonhead tensile specimens and isostatically pressed combustor tiles were developed and fabricated by Carborundum for the DOE/Solar Ceramic Stationary Gas Turbine (CSGT) development program. Tooling designs, processing details, material properties, and nondestructive evaluation (NDE) procedures are discussed. Post-sinter hot isostatic pressing (HIPing), which improves density, strength and uniformity, was done on all components. Both injection-molded and isopressed flexure bars produced strengths in excess of 621 MPa (90 ksi), while the fast-fracture tensile strength of injection-molded HEXOLOY® SA SiC was 453 MPa (66 ksi). The injection-molding and isopressing process changes leading to HEXOLOY® SA SiC strength increases are discussed, a recent properties summary on delivered test specimens is given, the buttonhead tensile specimen and combustor tile processing issues are described, and proposed process modifications to enhance fabrication economics are suggested.
Measurements of the Tip-Leakage Flow in a Turbine Cascade With Large Clearances
Authors: De Cecco S. , Yaras M. I. , Sjolander S. A.
Published: February 2015

Measurements have been made for tip clearances up to 15% of chord in a turbine cascade which has been used previously to study the tip-leakage flow at smaller clearances. The work is part of a study of the aerodynamics of turbines which have experienced in-service damage and is related to Engine Health Monitoring. Detailed flow field measurements have been made upstream and downstream of the cascade and static pressure distributions have been measured on the endwall and at the midspan of the blade. The most unexpected result was that the blade end losses (that is, the sum of the secondary and tip-leakage losses) reached a maximum for a clearance of about 6% of chord. At the largest clearance of 15%, the end losses were substantially reduced and were in fact comparable with the secondary losses measured for zero clearance. The paper discusses in some detail the physics of the flow and the reasons for the observed reduction in losses. The pressure difference across the gap was found to be considerably attenuated at the largest clearance. This would have the effect of reducing the mass flow rate per unit area through the gap as well as the kinetic energy of the gap flow. These effects appear to account for a large part of the reduction in losses. As might be expected, the turning of the flow near the endwall was considerably reduced at the large clearances.
A Navier Stokes Computer Code for Theoretical Investigations on the Applicability of Various Turbulence Models for Flow Prediction Along Turbine Blades
Authors: Bohn Dieter , Emunds Rolf
Published: February 2015

The quality of theoretical flow prediction in turbomachines is strongly influenced by the modeling of the turbulent fluctuations. These fluctuations are generated by various secondary flow mechanisms, the swirl of the flow occuring in blade channels and the curvature of the streamlines. Furthermore, the character of turbulence can become highly anisotropic indicating that the well known algebraic and two-equation k-ε type models might become unserviceable.

The present paper deals with the validation of a fully implicit 2-D steady-state Navier-Stokes algorithm and the comparison of the applicability of various turbulence models for predicting the flow along the blades of a turbine nozzle.

In the first section a short review is given on the basic numerical assumptions of the used computer code and on the employed two layer algebraic, one- and two-equation turbulence models. The influence of the fully implicitly formulated transport equations for the turbulent quantities, especially the influence of the discretization of the production and dissipation terms on the stability of the numerical scheme is pointed out. The validation of the numerical algorithm is done for an inviscid flow through the Hobson 2 impulse cascade, for the turbulent flow over a flat plate and for the flow through a turbine stator channel.

In a last section results obtained from calculations for a subsonic turbine stator flow inside and downstream of the blade passage with several turbulence models are presented. The apparent differences, especially in the distribution of the total pressure loss downstream of the trailing edge are discussed.
Launching of Single, Small Particles for Impact FOD Testing of Ceramic Gas Turbines
Authors: Yoshida Hiro , Uematsu Kazuo , Burie Alain
Published: February 2015

In developing ceramic gas turbines (CGT), impact test technique of ceramic elements at elevated temperature (sometime with tensile stress) is very important. For the purpose of establishing an impact simulation technique for small, foreign object damage (FOD) without contamination of testing environment, launch experiment of single particle of 1 mm diameter is made by using micro-sabot and electrothermal (ET) gun. Since the ET gun exhausts only small amount of gases, it is expected not to disturb temperature condition of testing environment. Particle velocity is measured by various methods based on 1) time difference between impact acoustic signals at muzzle and target, 2) high-speed photographs, and 3) induction current signal from coil-magnet flyer particle system. First particle is mounted on the micro-sabot and accelerated together. Then they are separated by sabot stopper placed at the ET gun muzzle. In the present experiments particle velocities up to about 2,000 m/s are obtained. However, complete separation of particle and sabot, where no sabot fragments appear from the muzzle, is possible up to about 1,000 m/s within the present separation system. This velocity range covers the required one (≦ 800 m/s). By using the launch system, impact tests of the actual turbine CGT-303 are carried out at room temperature without any loads. The tests at elevated temperature with tensile stresses are scheduled in the near future.
Theoretical and Experimental Comparisons for Damping Coefficients of a Short Length Open-End Squeeze Film Damper
Authors: San Andres Luis A.
Published: February 2015

Squeeze film dampers (SFD) provide load isolation and attenuate rotor vibrations in high speed turbomachinery. Operating parameters such as whirl frequency, amplitude of journal motion and value of external pressure supply determine the SFD dynamic force response and its dissipation of mechanical energy. Measurements of pressure fields and fluid film forces in a fully submerged open end - squeeze film damper are presented for tests with rotor speeds to 5,000 cpm and low supply pressures. The damper has a clearance of 381 µm (0.015 in) and the journal describes circular centered orbits of amplitudes ranging from 30% to 50% of the bearing clearance. Experimental film pressures depict a vapor cavitation (close to zero absolute pressure) zone increasing in extent as the whirl frequency increases. Estimated fluid film forces from the measured pressure profiles are found to be proportional to whirl speed and lubricant viscosity. Test cross coupled damping coefficients (Cπ) are smaller than predicted values based on the short length bearing model with a π film cavitation assumption. The direct damping coefficients (Cπ) are larger than theoretical values, especially at low frequencies where the dynamic cavitation region has not grown to half the circumferential flow extent. The experiments demonstrate the viscous character of the fluid film forces in a SFD test apparatus where fluid inertia effects are minimal (squeeze film Reynolds number less than one). On the other hand, the extent of the cavitation zone appears to be dominant on the generation of fluid film forces.
Feasibility Study on Oil Droplet Flow Investigations Inside Aero Engine Bearing Chambers: PDPA Techniques in Combination With Numerical Approaches
Authors: Glahn A. , Kurreck M. , Willmann M. , Wittig S.
Published: February 2015

The present paper deals with oil droplet now phenomena in aero engine bearing chambers. An experimental investigation of droplet sizes and velocities utilizing a Phase Doppler Particle Analyzer (PDPA) has been performed for the first time in bearing chamber atmospheres under real engine conditions.

Influences of high rotational speeds are discussed for individual droplet size classes. Although this is an important contribution to a better understanding of the droplet flow impact on secondary air/oil system performance, an analysis of the droplet flow behaviour requires an incorporation of numerical methods because detailed measurements as performed here suffer from both strong spatial limitations with respect to the optical accessibility in real engine applications and constraints due to the extremely time consuming nature of an experimental flow field analysis. Therefore, further analysis is based on numerical methods. Droplets characterized within the experiments are exposed to the flow field of the gaseous phase predicted by use of our well-known CFD code EPOS. The droplet trajectories and velocities are calculated within a Lagrangian frame of reference by forward numerical integration of the particle momentum equation.

This paper has been initiated rather to show a successful method of bearing chamber droplet flow analysis by a combination of droplet sizing techniques and numerical approaches than to present field values as a function of all operating parameters. However, a first insight into the complex droplet flow phenomena is given and specific problems in bearing chamber heat transfer are related to the droplet flow.
Phase Averaged Wall Shear Stress, Wall Pressure and Near Wall Velocity Field Measurements in a Whirling Annular Seal
Authors: Morrison Gerald L. , Winslow Robert B. , Thames H. Davis
Published: February 2015

The flow field inside a 50% eccentric whirling annular seal operating at a Reynolds number of 24,000 and a Taylor number of 6,600 has been measured using a 3-D laser Doppler anemometer system. Flush mount pressure and wall shear stress probes have been used to measure the stresses (normal and shear) along the length of the stator. The rotor was mounted eccentrically on the shaft so that the rotor orbit was circular and rotated at the same speed as the shaft (a whirl ratio of 1.0). This paper presents mean pressure, mean wall shear stress magnitude and mean wall shear stress direction distributions along the length of the seal. Phase averaged wall pressure and wall shear stress are presented along with phase averaged mean velocity and turbulence kinetic energy distributions located 0.16c from the stator wall where c is the seal clearance. The relationships between the velocity, turbulence, wall pressure and wall shear stress are very complex and do not follow simple bulk flow predictions.
An Experimental and Numerical Study of the Isothermal Flowfield Behind a Bluff Body Flameholder
Authors: Raffoul Charbel N. , Nejad Abdollah S. , Gould Richard D. , Spring S. Alan
Published: February 2015

An experimental and numerical investigation was conducted to study the turbulent velocities and stresses behind a 2-D bluff body. Simultaneous three-component laser Doppler velocimeter (LDV) measurements were made in the isothermal incompressible turbulent flowfield downstream of a bluff body placed at midstream in a rectangular test section. Mean velocities and Reynolds stresses were measured at various axial positions. Spanwise velocity measurements indicated that the flow is three dimensional in the recirculation zone of the bluff body. Confidence in the accuracy of the data was gained by calculating the mass fluxes at each axial station. These were found to agree with each other to within ±3%. A parallel Computational Fluid Dynamics (CFD) study was initiated to gauge the predictive accuracy of currently available CFD techniques. Three solutions were computed: a 2-D steady-state solution using the standard k-ε model, a 2-D time-accurate solution using the standard k-ε model, and a 2-D time-accurate solution using a Renormalized-Group (RNG) k-ε turbulence model. The steady-state solution matched poorly with the data, severely underpredicting the Reynolds stresses in the recirculation zone. The time-accurate solutions captured the unsteady vortex shedding from the base of the bluff body, providing a source for the higher Reynolds stresses. The RNG k-ε solution provided the best match to the data.
Topping Combustor Status for Second Generation Pressurized Fluidized Bed Cycle Application
Authors: Domeracki William F. , Dowdy T. E. , Bachovchin Dennis M.
Published: February 2015

Second-Generation Pressurized Fluidized Bed (PFB) combined cycles employ topping combustion to raise the turbine inlet temperature for enhanced cycle efficiency. This concept creates special combustion system requirements that are very different from requirements of conventional gas turbine systems. The topping combustor provides the means for achieving state-of-the-art turbine inlet temperatures and is the main contributor to enhanced plant performance. The objective of this program is to develop a topping combustor that provides low emissions, and is a durable, efficient device exhibiting stable combustion and manageable wall temperature. The combustor will be required to burn a low-Btu syngas under normal “coal-fired” conditions. However, for start-up and/or carbonizer outage, it may be necessary to fire a clean fuel, such as, oil or natural gas.

Prior testing has shown the Westinghouse Multi-Annular Swirl Burner (MASB) to have excellent potential for this application. Metal wall temperatures can be maintained at acceptable levels, even though most “cooling” is done by 1600°F vitiated air. Good pattern factors and combustion efficiencies have been obtained. Additionally, low conversion rates of fuel bound nitrogen to NOx have been demonstrated.

This paper presents an update of the status of an ongoing topping combustor development and test program for application to “Second Generation Pressurized Fluidized Bed Combined Cycles (PFBCC).” The program is sponsored by the Department of Energy’s Morgantown Energy Technology Center (DOE/METC) and will first be applied commercially into the Clean Coal Technology Round V Four Rivers Energy Modernization Project. Phase 1 of the program involved a conceptual and economic study (Robertson et al., 1988); Phase 2 addresses design and subscale testing of components; and Phase 3 will cover pilot plant testing of components integrated into one system.
A NOx Prediction Scheme for Lean-Premixed Gas Turbine Combustion Based on Detailed Chemical Kinetics
Authors: Polifke Wolfgang , Döbbeling Klaus , Sattelmayer Thomas , Nicol David G. , Malte Philip C.
Published: February 2015

The lean-premixed technique has proven very efficient in reducing the emissions of oxides of nitrogen (NOx) from gas turbine combustors. The numerical prediction of NOx-levels in such combustors with multidimensional CFD codes has only met with limited success so far. This is at least to some extent due to the complexity of the NOx formation chemistry in lean-premixed combustion, i.e. all three known NOx formation routes (Zeldovich, nitrous and prompt) can contribute significantly. Furthermore, NOx formation occurs almost exclusively in the flame zone, where radical concentrations significantly above equilibrium values are observed.

A relatively large chemical mechanism is therefore required to predict radical concentrations and NOx formation rates under such conditions. These difficulties have prompted the development of a NOx post-processing scheme, where rate and concentration information necessary to predict NOx formation is taken from one-dimensional combustion models with detailed chemistry and provided — via look-up tables — to the multi-dimensional CFD code.

The look-up tables are prepared beforehand in accordance with the operating conditions and are based on CO concentrations, which are indicative of free radical chemistry. Once the reacting flow field has been computed with the main CFD code, the chemical source terms of the NO transport equation, i.e. local NO formation rates, are determined from the reacting flow field and the tabulated chemical data. Then the main code is turned on again to compute the NO concentration field. This NOx sub-model has no adjustable parameters and converges very quickly. Good agreement with experiment has been observed and interesting conclusions concerning superequilibrium O-atom concentrations and fluctuations of temperature could be drawn.
Study of Flame Stability in a Step Swirl Combustor
Authors: Durbin Mark D. , Vangsness Marlin D. , Ballal Dilip R. , Katta Viswanath R.
Published: February 2015

A prime requirement in the design of a modem gas turbine combustor is good combustion stability, especially near lean blowout (LBO), to ensure an adequate stability margin. For an aeroengine, combustor blow-off limits are encountered during low engine speeds at high altitudes over a range of flight Mach numbers. For an industrial combustor, requirements of ultra-low NOx emissions coupled with high combustion efficiency demand operation at or close to LBO. In this investigation, a step swirl combustor (SSC) was designed to reproduce the swirling flow pattern present in the vicinity of the fuel injector located in the primary zone of a gas turbine combustor. Different flame shapes, structure and location were observed and detailed experimental measurements and numerical computations were performed.

It was found that certain combinations of outer and inner swirling air flows produce multiple attached flames, a flame with a single attached structure just above the fuel injection tube, and finally for higher inner swirl velocity, the flame lifts from the fuel tube and is stabilized by the inner recirculation zone. The observed difference in LBO between co- and counter-swirl configurations is primarily a function of how the flame stabilizes i.e., attached vs. lifted. A turbulent combustion model correctly predicts the attached flame location(s), development of inner recirculation zone, a dimple-shaped flame structure, the flame lift-off height, and radial profiles of mean temperature, axial velocity, and tangential velocity at different axial locations. Finally, the significance and applications of anchored and lifted flames to combustor stability and LBO in practical gas turbine combustors are discussed.
Differential Mass and Energy Balances in the Flame Zone From a Practical Fuel Injector in a Technology Combustor
Authors: Warren David L. , Hedman Paul O.
Published: February 2015

This paper presents further analysis of experimental results from an Air Force program conducted by researchers at Brigham Young University (BYU) Wright-Patterson Air Force Base (WPAFB), and Pratt and Whitney Aircraft Co. (P&W) (Hedman, et al., 1994a and 1994b). These earlier investigations of the combustion of propane in a practical burner installed in a technology combustor used: 1) digitized images from video and still film photographs to document observed flame behavior as fuel equivalence ratio was varied, 2) sets of LDA data to quantify the velocity flow fields existing in the burner, 3) CARS measurements of gas temperature to determine the temperature field in the combustion zone, and to evaluate the magnitude of peak temperature, and 4) two-dimensional PLIF images of OH radical concentrations to document the instantaneous location of the flame reaction zones.

This study has used the in situ velocity and temperature measurements from the earlier study, suitably interpolated, to determine local mass and energy balances on differential volume elements throughout the flame zone. The differential mass balance was generally within about ± 10% with some notable exceptions near regions of very high shear and mixing. The local differential energy balance has qualitatively identified the regions of the flame where the major heat release is occurring, and has provided quantitative values on the rate of energy release (up to −400 kJ/m3s).

The velocity field data have also been used to determine Lagrangian pathlines through the flame zone. The local velocity and temperature along selected pathlines have allowed temperature timelines to be determined. The temperature generally achieves its peak value, often near the adiabatic flame temperature, within about 10 ms. These temperature timelines, along with the quantitative heat release data may provide a basis for evaluating kinetic combustion models.
A Method for Predicting Inlet Temperature Distortion Caused by Missile Plumes
Authors: Shuo Wang , Xijun Huang , Jiya Cui , Changtian Luo
Published: February 2015

In this paper we provide information for the design of a 3D external compression inlet system which is affected by the exhaust plume of a missile. The inlet 3D flow field has been simulated by 3D time dependent Euler equations and solved using the J. D. Denton scheme. The total temperature and total pressure distributions are obtained for a quasi–steady state and the temperature increment (DT) and its variation rate (RDT) are calculated. Two definitions of DT and RDT are given and a simple condition has been put forward for calculating the inlet flow field with serious upstream distortion. Finally, an attenuation law is presented which estimates the temperature distortion in the inlet duct from the inlet entrance to the exit for different conditions and different intervals.
Engine Test Facility Dynamic Data Systems Upgrade and Improvement Plan
Authors: Jones Henry T.
Published: February 2015

The Engine Test Facility (ETF) at Arnold Engineering Development Center (AEDC) has many test cells supported with instrumentation systems for acquiring, monitoring, recording, and processing dynamic data. These systems must be updated to meet rapidly changing requirements to acquire more data at increased band-widths, increase online monitoring information, and provide rapid data processing for shortening data turnaround time.

This paper presents the rationale and plans for converting from a dynamic data system centered around analog data recorders to a digital-based system using high-density digital recorders. Transition to the digital-based system is planned over a five-year period. The current dynamic data systems are described, new technologies in advanced online monitoring systems are identified, and centralization of online monitoring stations and digital data recorders with robotic tape storage and retrieval capabilities are recommended.
Application of the Time Linearized Euler Method to Flutter and Forced Response Calculations
Authors: Kahl G.
Published: February 2015

The Time Linearized Euler Method has proven to be a useful design tool, capable of predicting unsteady flows in turbomachinery within the accuracy required for engineering purposes while being fast enough for routine use in the design process.

This paper first briefly describes the approach and its implementation in the current method. A range of applications of the method is described for flutter calculations in turbines and compressors with different levels of complexity such as chord wise bending, single or clustered airfoils, sub- or transonic flow. Farced response calculations are shown for airfoils passing through wakes and for a rotor operating in the pressure field of a downstream outlet guide vane. The results are presented as aerodynamic damping, unsteady work distributions and unsteady flowfield plots. Data shown includes information on boundary conditions, mesh size, computation time and convergence histories.

The paper provides insight into an industry approach to modeling unsteady turbomachinery flows.
Effects of Free Stream Turbulence on Intermittent Boundary Layer Flows
Authors: Kalfas Anestis I. , Elder Robin L.
Published: February 2015

This paper considers the effects of free stream turbulence intensity on intermittent boundary layer flows related to turbomachinery. The present experimental investigation has been undertaken under free stream flow conditions dominated by grid generated turbulence and Reynolds numbers appropriate for turbomachinery applications. Unseparated flow transition in the boundary layer has been considered using a flat plate with the C4 leading edge which has been designed to avoid laminar separation. This configuration provided the opportunity to study the effect of a realistic turbomachinery leading edge shape on transition. Boundary layer type hot-wire probes have been used in order to acquire detailed information about the effect of the free stream conditions and the leading edge configuration on the structure of the boundary layer. Furthermore, information about the intermittency distribution throughout the boundary layer has been obtained using statistical analysis of the velocity record of the flow field.
Comparison of Test Measurements Taken on a Pipeline Compressor / Gas Turbine Unit in the Workshop and at Site
Authors: Schmitt W. , Thomas V.
Published: February 2015

The first part of this paper describes the test installation of the gas turbine and the compressor in the workshop, test execution, measuring methods, evaluation and measuring uncertainties.

The second part of this paper describes the site installation, execution of the test under full load conditions on natural gas, measuring methods, evaluation and measuring uncertainties.

The third part of this paper compares both the measurements and the Reynolds number correction which was used for the evaluation of the pipeline compressor test results in the workshop.
Development of a Wide Range Temperature Pyrometer for Gas Turbine Application
Authors: Moon H. K. , Glezer B. , Mink B. , Marvin W.
Published: February 2015

The applications of optical pyrometry in gas turbines are diverse. Optical pyrometry provides many advantages over other techniques for temperature measurement. The inherent problems associated with low temperature measurement have limited optical pyrometry equipment for the hot cascade and low temperature turbine component applications. Traditional uses of this type of equipment have been limited to high temperature (>600°C) measurements. A wide range temperature pyrometer (>230°C) with unique design concepts was developed to address these issues. The pyrometer effectively operated in a long wavelength (2.00 to 2.25 mm) radiation to measure a relatively low temperature, as well as avoid the absorption bands of the gases commonly present in gas turbines. It was analytically and experimentally proven that the pyrometer was practically insensitive to the distance and view angle. The pyrometer was calibrated in a controlled-temperature model, and its reliability and applicability were demonstrated in a hot cascade environment.
Prediction of Unshrouded Rotor Blade Tip Heat Transfer
Authors: Ameri A. A. , Steinthorsson E.
Published: February 2015

The rate of heat transfer on the tip of a turbine rotor blade and on the blade surface in the vicinity of the tip, was successfully predicted. The computations were performed with a multiblock computer code which solves the Reynolds Averaged Navier-Stokes equations using an efficient multigrid method. The case considered for the present calculations was the SSME (Space Shuttle Main Engine) high pressure fuel side turbine. The predictions of the blade tip heat transfer agreed reasonably well with the experimental measurements using the present level of grid refinement. On the tip surface, regions with high rate of heat transfer was found to exist close to the pressure side and suction side edges. Enhancement of the heat transfer was also observed on the blade surface near the tip. Further comparison of the predictions was performed with results obtained from correlations based on fully developed channel flow.
Recent Advances in Gas Turbine Engine Dynamic Models Developed Through JDAPS
Authors: Garrard G. D. , Davis M. W. , Hale A. A.
Published: February 2015

The Joint Dynamic Airbreathing Propulsion Simulation (JDAPS) partnership was formed far the purpose of developing, validating, and applying advanced analytical simulations to investigate gas turbine engine dynamic performance and operability. This paper provides an introduction and demonstrates the operation of three dynamic models and simulations developed by members of the JDAPS partnership. These dynamic models and simulations include a new combustor analysis program (VP1COMB), the integration of the dynamic combustor model into an existing dynamic stage-by-stage compressor model and simulation (DYNTECC), and a new full gas turbine engine dynamic model and simulation (ATEC). For each of the gas turbine engine analysis tools, the model equations are first introduced, then operation of the simulation is demonstrated through selected test cases. The simulation results obtained during the operational verification test cases were appropriate for the inputs given. Calibration of the models and simulations has only been accomplished in a limited manner to date and will be the topic of future papers.
Indirect Turbulence Measurement in Gas Turbine Stages Using Heat Flux Probe
Authors: Zhang Luzeng J. , Glezer Boris
Published: February 2015

An experimental study with the application of a custom designed heat flux probe and a modified Kiel probe to measure the turbulence intensity along the turbine gas path downstream of the combustor was performed in an industrial gas turbine engine. The probes were calibrated in a hot-cascade facility test rig which closely emulates engine operating conditions, particularly Re number and Mach number. Correlations based on the test results were compared with the data available in the literature. Indirect turbulence measurements performed in gas turbine engines show that the turbulence intensity at the combustor exit for different combustors can vary from 8% to 12% and the turbulence intensities (combined mainstream and wake generated turbulence) downstream from first and second stage blades can reach 12% to 18%. The results show that the unsteady wakes generated from upstream blade trailing edge play a major role in the turbulence augmentation on downstream nozzle heat transfer. A similar effect is expected in the turbine blade leading edge with a wake turbulence generated by the trailing edge of the upstream vane. An established correlation allows the prediction of a combined turbulence intensity along the gas path when initial combustor mainstream turbulence intensity and engine design parameters are defined (rotating speed, number of airfoils, trailing edge diameter, mainstream velocity, etc.).
Off-Design Performance of Multipressure Heat Recovery Boilers
Authors: Bettagli Nicola , Facchini Bruno
Published: February 2015

Combined cycle power plants are systems with very high thermodynamic efficiency. Off-design plant behaviour prediction is very important to allow for high efficiency regulation of systems.

The aim of this paper is to study heat recovery steam generator (HRSG) performance, varying inlet gas temperature and mass flow rate. One, two and three pressure level heat recovery boilers are considered. A HRSG simulation program based on heat transfer and thermodynamic fundamental laws is carried out.