bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Swirl and Wall Geometry on the Emissions of Advanced Gas Turbine Combustors
Authors: Micklow Gerald J. , Shivaraman Karthikeyan
Published: February 2015

A numerical study was performed to investigate the chemically reactive flow with liquid spray injection in a staged combustor concept for reducing pollutant emissions. The staged combustor consists of an airblast atomizer, a rich bum section, a converging connecting pipe, a quick mix zone, a diverging connecting pipe, and a lean combustion zone. For computational efficiency, the combustor was split into two subsystems, i.e. the fuel nozzle/rich burn section and the quick quench/lean bum section.

The current study investigates the effect of wall geometry and swirl direction, i.e. co- or counter-rotating swirl, on fuel distribution, temperature distribution, and emissions for the fuel nozzle/rich bum section at a cruise condition. At an equivalence ratio of 1.9, the nozzle-combustor (dome) interface geometry was varied from a flat wall (normal to the combustor wall) to a sloped wall of 45 degrees. It is seen that the sloped wall with co-rotating swirl direction had a substantial effect on combustor performance and reducing pollutant emissions.
Effects of Buoyancy on Heat Transfer and Oxygen Consumption in Fuel-Thermal-Stability Studies
Authors: Katta Viswanath R. , Blust James W. , Williams Theodore F. , Martel Charles R.
Published: February 2015

A unique methodology is used to investigate the effects of gravity on fuel flowing through the small-bore heated tubes that are often used in the study of fuel-thermal-stability characteristics. The copper block that houses the fuel tube (or test section) is located on a swivel, and experiments are conducted for different tube orientations namely; horizontal, vertical with flow from bottom to top and vice versa. Results obtained for different fuel-flow rates and block temperatures are discussed. An axisymmetric, time-dependent numerical model is used to simulate the flow patterns in the test section. This model solves momentum, energy, species and k-ε turbulence equations. The buoyancy term is included in the axial-momentum equation. Natural flow resulting from buoyancy was found to have a significant effect on heat transfer and oxygen consumption for fuel-flow rates up to 100 cc/min (Reynolds numbers up to 2300). Flow instabilities were observed when the fuel was flowing downward in a vertically mounted test section. The effect of block temperature and flow rate on these instabilities was also studied.
Characterization of the Non-Reacting Two-Phase Flow Downstream of an Aero-Engine Combustor Dome Operating at Realistic Conditions
Authors: McDonell Vincent G. , Seay Jason E. , Samuelsen Scott
Published: February 2015

The structure of the two-phase flow produced by a SNECMA/GEAE CFM-56 swirl cup is characterized using flow visualization and phase Doppler interferometry. Three operating conditions are examined, corresponding to 3.5, 7, and 15% power levels for the engine. Detailed measurements are obtained for the 3.5 and 7% power conditions. The results obtained are contrasted to previous results obtained in an idealized environment with the goal of assessing the relevance of such data to practical conditions. The results reveal that the increase in power has little impact upon the general structure of the flow and that even the atmospheric results provide the basic structure associated with the actual conditions. This is attributed to the similarity in pressure drop for each of the cases considered. Increasing power does lead to a systematic reduction in drop size despite exceeding crossover points for the duplex atomizer used. This difference is attributed primarily to inlet temperature changes.
A Gas Turbine Blade Thermal/Structural Program With Linked Flow-Solid Modeling Capability
Authors: Wan S. M. , Lam T. C. T. , Allen J. M. , McCloskey T. H.
Published: February 2015

A time-marching approach is adopted in developing a thermal/structural program with linked flow-solid modeling capability. The Blade Life Analysis & Design Evaluation for Combustion Turbines (BLADE-CT) program analyzes gas turbine blade thermal-mechanical stress and natural frequencies under the boundary conditions which result from the gas flow and the cooling/barrier flow within a given turbine stage. Using the finite element method, the blade temperatures obtained from transient/steady-state thermal solutions can be utilized to compute thermal stresses and dynamic stresses under operating conditions for assessing thermal-mechanical fatigue damage in combustion turbine blades. A customized and automated mesh generation routine is developed to model cooled (spanwise multihole configurations) and solid gas turbine blades. By coupling the NASA flow programs, PCPANEL (potential flow), STAN5 (heat transfer boundary layer), and CPF (coolant passage flow) as part of an automated flow-structural analysis approach, a more efficient and accurate thermal and thermal stress calculation can be achieved. The calculated blade temperatures can be also applied for the frequency analysis to account for temperature effects. The coupled fluid-structure interaction program approach for thermal-mechanical analysis and an example of a spanwise cooled blade steady state analysis are presented.
Optimization of Rotor-Stator-Strut Potential Flow Interaction Including Rotor Feedback Effects
Authors: Cerri G. , Boatto P. , O’Brien W. F. , Sorrenti A.
Published: February 2015

A method for the optimization of stator blade stagger angles and of strut circumferential position in order to shield a rotor cascade from downstream strut pressure disturbances is presented. Potential flow interaction between rotor, stator and strut rows is analyzed by a boundary integral method for unsteady incompressible 2-D flows, based on singularity superposition over every blade profile. The flow field is solved in terms of velocity, and the pressure field is computed using the unsteady Bernoulli equation. An optimization technique based on a constrained minimization problem is applied; objective functions related to pressure coefficient and lift coefficients are considered. Force coefficients in the tangential and axial directions, and the momentum coefficient acting on the blades are calculated by integrating the pressure distribution over the blade profile. Results of the stagger angle and strut position optimization are presented and discussed. An analysis in the frequency domain is also performed.
Investigations Relating to the Effects of Various Internal Geometries on the Effectiveness of an Aero-Engine Intake Thermal Anti-Icing System
Authors: Riley S. J. , James E. H.
Published: February 2015

Various nose cowl internal geometry designs have been investigated in a study relating to the effect of hot air mass flows in the prevention of ice formation on the external nose cowl (lipskin) surfaces of aero-engine intakes. Significant differences in the lipskin surface temperature levels were observed as the internal, hot, anti-icing air distribution geometry was altered. A double-skinned arrangement (in which the hot air was closely confined to the region requiring protection against ice formation) was observed to be particularly advantageous in this respect. The effectiveness of this design was matched however by a conventional “piccolo” pipe distribution system whilst the remaining two internal Builds investigated were found to be not as effective. In evaluating the benefits that accrue from a particular design, factors such as weight, cost, reliability, maintenance and in-service experience must also be considered.
Comparison of Liquid Fuel/Air Mixing and NOx Emissions for a Tangential Entry Nozzle
Authors: Snyder Timothy S. , Rosfjord Thomas J. , McVey John B. , Chiappetta Louis M.
Published: February 2015

An experimental program was conducted to develop a technique for designing a dry low NOx liquid fuel injection configuration for a tangential entry lean-premixed fuel nozzle. Calculations were performed to predict the effect of liquid fuel injection location, orifice size and spacing, and initial droplet size on the vaporized fuel/air mixture uniformity exiting the highly-swirled premixing nozzle. Combustion tests were conducted at pressures ranging from 10–18 atm, and inlet temperatures ranging from 650–730 K, for the different liquid fuel injection schemes analyzed from the mixing study. Liquid fuel injection configurations that were predicted to give the best fuel/air distribution generated the lowest levels of NOx. The calculated fuel/air uniformity was a weak function of the spatial density of liquid fuel injection sites and the method of injecting the liquid fuel. The injection location and initial droplet size have the greatest impacts on fuel/air uniformity. The analysis indicated that 40 micron diameter droplets mix adequately while larger droplets (80 micron) are centrifuged out of the main body of the flow and produce locally high fuel/air ratios. The NOx levels achieved for the best liquid fuel injection configuration approached those obtained for a well premixed gas fuel configuration using the same tangential entry nozzle.
Numerical Simulation of Blade Fault Signatures From Unsteady Wall Pressure Signals
Authors: Dedoussis V. , Mathioudakis K. , Papailiou K. D.
Published: February 2015

A method for establishing signatures of faults in the rotating blades of a gas turbine compressor is presented. The method employs a panel technique for the calculation of the flow field around blade cascades, with disrupted periodicity, a situation which is encountered when a blade fault has occurred. From this calculation, time signals of the pressure at a location on the casing wall, facing the rotating blades, are constituted. Processing these signals, in combination with “healthy” pressure signals allows the constitution of fault signatures. The proposed method employs geometrical data, as well as data about the operating point of the engine. It gives the possibility of establishing the fault signatures without the need of performing experiments with implanted faults. The successful application of the method is demonstrated by comparison of signatures obtained by simulation to signatures derived from experiments with implanted blade faults, in an industrial gas turbine.
Dynamic Control of Rotating Stall in Axial Flow Compressors Using Aeromechanical Feedback
Authors: Gysling D. L. , Greitzer E. M.
Published: February 2015

Dynamic control of rotating stall in an axial flow compressor has been implemented using aeromechanical feedback. The control strategy developed used an array of wall jets, upstream of a single-stage compressor, which were regulated by locally reacting reed valves. These reed valves responded to flowfield pressure perturbations associated with the small amplitude perturbations that precede rotating stall. The valve design was such that the combined system, compressor plus reed valve controller, was stable under operating conditions that had been unstable without feedback. A 10% decrease in the stalling flow coefficient was achieved using the control strategy, and the stable flow range was extended with no noticeable change in the steady state performance of the compression system.

The experimental demonstration is the first use of aeromechanical feedback to extend the stable operating range of an axial flow compressor. It is also the first use of local feedback and dynamic compensation techniques to suppress rotating stall.

The design of the experiment was based on a two-dimensional stall inception model which incorporated the effect of the aeromechanical feedback. The physical mechanism for rotating stall in axial flow compressors was examined with focus on the role of dynamic feedback in stabilizing compression system instability. The effectiveness of the aeromechanical control strategy was predicted, and experimentally demonstrated, to depend on a set of non-dimensional control parameters that determine the interaction of the control strategy and the rotating stall dynamics.
The Application and Experience of HVOF Coatings in the Repair and Overhaul of Industrial Gas Turbines
Authors: Smith C. W. , Naisbitt G.
Published: February 2015

High Velocity Oxy-Fuel thermal spray systems (HVOF), also known as High Velocity Combustion systems (HVC) are high energy thermal spray combustion processes, producing very hard, high density coatings. These coatings are used in areas where high wear resistance is of particular importance, with metal carbide coatings being typical in gas turbine applications.

Gas turbines use hard face coatings in such areas where vibration is the initial source of the problem. The areas tend to be in the hot end of the gas turbines although certain areas of the cold end are also affected. To date the hard face coating that has been predominately applied in gas turbines particularly in the hot end, is the Praxair (Union Carbide) “D” gun coating. As a result to date, the “D” gun system has had a virtual monopoly with regards to the overhaul/repair of gas turbine components where hard face coating was required.

However new HVOF systems have come on to the market Examples are: CDS, Plasma Technik; Diamond Jet, Metco; Top Gun, UPT U.K. (Miller); Jet Kote, Deloro Stellite; Gun. Metallisation and JP 5000, Hobart Tafa. As a result gas turbine overhaul bases are now in a position to offer a more competitve coating service, producing comparable, and in some cases superior, coatings to those produced by the “D” gun process.

This paper covers, from the Rolls Wood Group point of view, the developments of the HVOF systems, where they appear to be today and how these systems, now allow overhaul bases to offer services not previously available and the ability to develop new coating applications.
Advanced GT’s Call for Advanced CC’s (OR: the 4 S’s)
Authors: Jury Walter , Luthi Hans K.
Published: February 2015

Four key parameters, the 4 S’s, determine the technoeconomical performance of the steam bottoming cycle to a given gasturbine: [S1], the temperature of the heat Source, [S2], the temperature of the heat Sink, [S3] cycle Structure and [S4] component Specifications. The first two are given by the gasturbine exhaust gas temperature (TEX) and ambient water/air temperatures respectively; the last two are designer’s choice but depend on economics: how much can you afford to pay for an extra kW? (parity factor or differential capital outlay).

The paper analyses the effect of current trends in the first two S’s on the latter two: «S1», the higher TIT (turbine inlet temperature) of advanced GT’s generally leads to higher TEX, especially when coupled with Sequential Combustion; and [S2]«S2», the trend from fresh water cooling to cooling towers — and again from wet to dry types — due to environmental considerations and/or water shortages leads to higher condenser pressures. These trends change the economics of «S3», the structure (one-, two- or three-pressure, reheat, supercritical etc.); finally, macro-economical trends (fuel cost, cost of capital, more Independent Power Producers or IPP’s) determine «S4», equipment specifications (delta-T’s, delta-P’s, number of stages or exhaust flows etc.).

In this written paper the authors report on their technoeconomical analysis; at the conference they will present hands-on solutions, optimized for ABB’s Type GT24 (60Hz, 165 MW) and GT26 (50 Hz, 240 MW) gasturbines. (Note that throughout the paper definite figures are only given for ABB gasturbines and steam turbines, as the authors cannot vouch for information published by other manufacturers or third parties).
A Review of the Efficacy of Silicon Carbide Hot Gas Filters in Coal Gasification and Pressurized Fluidized Bed Combustion Environments
Authors: Judkins Roddie R. , Stinton David P. , DeVan Jackson H.
Published: February 2015

Reviews of relevant literature and interviews with individuals cognizant of the state-of-the-art in ceramic filters for hot-gas cleaning were conducted. Thermodynamic calculations of the stability of various ceramic phases were also made. Based on these calculations, reviews, and interviews, conclusions were reached regarding the use of silicon carbide-based ceramics as hot-gas filter media. Arguments are presented that provide the basis for our conclusion that high-purity silicon carbide is a viable material in the integrated coal gasification combined cycle (IGCC) and pressurized fluidized-bed combustion (PFBC) environments we examined. Clay-bonded materials are, we concluded, suspect for these applications, their extensive use notwithstanding. Operations data we reviewed focused primarily on clay-bonded filters, for which a great deal of experience exists. We used the clay-bonded filter experience as a point of reference for our review and analysis.
Development of an Acoustically Enhanced Cyclone Collector for PFBC
Authors: Gallca Marlene A.
Published: February 2015

Acoustically enhanced cyclone collectors offer the potential of achieving environmental particulate control standards under pressurized fluidized bed combustion (PFBC) conditions without the need for post turbine particulate control. The objective of this research program is to extend acoustic agglomeration technology from the laboratory scale up to the sub-pilot scale. The effects of high intensity sound on the agglomeration of fly ash particles are being investigated in a simulated PFBC effluent stream. The test facility consists of a variable residence time acoustic agglomeration chamber with a vitiating air preheat combustor, an ash injection system utilizing an auger feeder, a natural gas fired pulse combustor sound source, and a two-stage high temperature, high pressure cyclone. Fly ash for these tests has been obtained from the TVA (Tennessee Valley Authority) Shawnee Station circulating fluidized bed combustor (CFBC), as well as the Nucla CFBC, and Tidd PFBC. Acoustic agglomeration tests are underway.

The acoustically enhanced cyclone collector is being evaluated with two distinct goals in mind: 1) determine the effects of the major operating parameters on acoustic agglomeration efficiency, and 2) optimize the agglomeration system performance for maximum particulate removal efficiency. The data obtained during these tests will provide direct information on the effects of sound intensity and frequency, particle residence time, ash loading, and pressure on the enhancement of cyclone collection efficiency with acoustic agglomeration. These data, in conjunction with results from an acoustic agglomeration computer model will be used to evaluate the economic and engineering feasibility of an acoustically enhanced cyclone collector for a full scale pressurized fluidized bed combustor.
The Model V84.3 Shop Tests: Tip Clearance Measurements and Evaluation
Authors: Janssen M. , Seume J. , Zimmermann H.
Published: February 2015

The design of high-performance gas turbines requires the reliable prediction of blade tip clearances. Excess clearances allow a portion of the hot gas to flow over the blade tips without performing useful work. The tip leakage flow disturbs the flow field which results in additional losses. Moreover, insufficient blade tip clearance may cause interference which can reduce turbine life. In conventional turbomachines, the blade tip clearances vary markedly with the operating condition of the turbine, essentially as a result of variations in gas temperatures and rotor speed.

Siemens tests prototype gas turbines in its own test facility. An extensive experimental program is devised to verify design calculations regarding strength, aerodynamics and thermodynamics. Among other measurements, the minimum operating tip clearance is measured by abrasion pins. Electro-mechanical sensors measure transient tip clearance during a selected duty cycle consisting of turning-gear operation, cold start, idle operation, as well as part-load, full-load, and most importantly, hot-start. In the present paper, the compressor and turbine tip clearances measured during such a load cycle are compared with calculated predictions. The experimental instrumentation for the prototype gas turbine, as well as design calculations, are presented.

The results show that the new Model V84.3 gas turbine does not exhibit critically small clearances during cold start nor during hot-start due to the careful matching of magnitude and the time constants of the thermal expansion of the blades, discs, blade-ring carriers and casing.
On the Use of Direct and Inverse Numerical Flow Calculations for Supersonic Turbine Design
Authors: Pommel F.
Published: February 2015

A procedure for blade design, using a time marching method to solve the Euler equations in the blade-to-blade plane is presented. This procedure uses an Office Nationale d’Etude et de Recherches Aeronautique flow solver. The classical slip conditions (no normal velocity component along the blade profile) has been replaced by another boundary conditions in such a way that the required pressure may be imposed directly. The orignal direct code was therefore transformed into an inverse solver. The unknows are calculated on the blade wall using the so-called compatibility relations. The blade geometry is then modified by resetting the wall parallel to the new flow field. The results obtained with this design process for a supersonic turbine blade of a space turbopump is presented.
Stall Inception in a High-Speed Low Aspect Ratio Fan Including the Effects of Casing Treatments
Authors: Gorrell S. E. , Russler P. M.
Published: February 2015

The stall inception process in high-speed compressor components is important to understand in order to increase stage loading while maintaining stall margin. This paper presents the results of an in depth experimental investigation on the stall inception of a two stage, high-speed, low aspect ratio fan that is representative of current operational commercial and military fan technology. High-response static pressure measurements are presented which detail the stall inception process of the fan under various operating conditions. These conditions include: varied corrected speeds, a smooth case, a circumferential groove casing treatment, and a recirculating cavity casing treatment. Stage pressure characteristics and radial pressure ratio profiles are presented for the different operating conditions. The stage performance data, together with the static pressure data, are analyzed to provide a clear and thorough understanding of the stall inception process and how the process may vary under different conditions. Experimental results show that a stage may stall on the positive, neutral, or negative sloped part of the pressure characteristic. The three casing treatments had a significant effect on the rotor tip flow and these variations changed the stall inception path of the fan. Stall inception was characterized by the formation of a stall inception cell which grew to fully developed rotating stall. Properties affected by the changing tip flow include the stall inception duration, stall inception cell frequency, existence of modal waves, duration of modal waves, and modal wave frequency. In some instances modal waves appear to play a role in stall inception, in others they do not.
A Theory for the Hydrodynamic Performance of Centrifugal Pump Impellers in Stall
Authors: Dussourd Jules L. , Hermann Paul , Westhoff Paul E.
Published: February 2015

A computerized analysis is presented which may have the potential of calculating the performance of turbomachines operating in the stalled regime. The method however is still in its infancy in that here only radial impellers pumping incompressible fluids and working with the simplest of diffusers are considered.

The physical model consists of a rotating cascade which admits forward flows as well as backflows existing concurrently, both described as time steady jets and wakes flowing on two stream surfaces which must be in equilibrium. The losses for non-reattaching flows are mainly the result of momentum exchanges, making it possible to develop a model somewhat, but not entirely free of empirical quantities.

The sum of the physical constraints that must be satisfied form a system of nine simultaneous equations with nine variables. Their solutions are computerized for PC work. The output yields the internal pressures and velocity diagrams, including quantification of the forward and backward flows, suction line vortexing, cavitation and overall performance.

To the extent that it could be explored to date, corroboration against test pumps measurements shows promising agreement using as criteria the absorbed power and in a more preliminary way, the intensity of the suction pipe phenomena and the head-flow curves when appropriate. The corroborations however have been carried out only for a few pumps.
Design of a Gas Turbine Burning Explosive Fuel
Authors: Roy G. K.
Published: February 2015

The use of naphtha as gas turbine fuel has been limited. In advanced countries naphtha is usually cracked to produce gasoline, or ethylene which commands premium rates in the market. In developing countries like India, however, the scenerio is much different. The market for the cracked products is not abundant. In addition, the paucity of natural gas has rather forced the authorities of power plants to use naphtha as alternative gas turbine fuel.
When are Nonlinearities Important at Stall Inception?
Authors: McCaughan F. E.
Published: February 2015

Recent experimental work has shown that in some compressors, the nonaxisymmetric disturbance leading to loss of stability appears as a localised phenomena, rather than a travelling sine wave which spans the entire circumference, suggesting that nonlinear effects appear very early in the evolution of the disturbance. In a regime dominated by nonlinear effects, the Fourier modes used to describe the spatial structure of non-axisymmetric disturbances, obtained from either experimental data or numerical data produced by a model, can interact very early in the rotating stall inception process. In this paper, we determine which parameters affect the rate of interaction of the various modes in a study of the Moore-Greitzer (MG) model. The relevant parameters are related back to the physics of compressors. Though the stall inception process may well be three-dimensional and involve physics not captured by the quasi two dimensional MG model, this study is of interest to those who wish to detect and control the magnitude of nonaxisymmetric disturbances, in order to decrease the stall margin in a compression system. Any control strategy which depends on eight detecting devices around the annulus of the compressor can resolve only the first three spatial Fourier modes. If disturbances leading to compression system instability develop as spikes, this approach will be completely unsuccessful at detecting the disturbances while they are still small enough to be controlled. The problem is further exacerbated by temporal nonlinearities, that is, the operating point may be linearly stable, but may lose stability to larger disturbances. It is observed in experiments and the Moore-Greitzer model that the compressor loses stability before the throttle is closed past the peak of the performance curve. Both spatial and temporal nonlinearities are discussed.
A Unique Test Facility to Measure Particle Restitution and Fragmentation
Authors: Tan S. C. , Harris P. K. , Elder R. L.
Published: February 2015

This paper describes an experimental test facility for measuring particle restitution ratio and particle fragmentation where the turbulent effect of air has been minimised. The restitution ratios, which relate the particle rebound characteristics to the impact velocity (and angle), are used in a trajectory code so that rebound conditions can be calculated after a particle has collided with a wall surface. Trajectory calculations are often used to predict the separation performance of inertial particle separators in a design cycle without resorting to the expensive ‘cut and try’ method. A ‘coanda’ particle injector is used to separate particles from the airstream which then relies on its own inertia to collide with a target plate. Particle rebound occurred in an quiescent condition in a target chamber which has been isolated from the surroundings. The particle rebound velocity (and angle) is measured with a two-spot transit anemometer operating in the backscattered mode. Measurements are taken at about 1.0–1.5 mm from the target plate surface. The overall dimension of the test facility is relatively small (1.0 × 0.5 × 0.5 m) compared to a windtunnel facility due to the absence of an airflow. Some results are presented for certain materials showings the effect of impact velocity, angle and particle size.
Three-Dimensional Fibre-Optics LDV Measurements in the Endwall Region of a Linear Cascade of Controlled-Diffusion Stator Blades
Authors: Hobson G. V. , Dober D. M.
Published: February 2015

Measurements were taken of the vortex system and turbulent flow that results from the Interaction between a stator blade tip and the approaching endwall boundary layer in a linear cascade of controlled-diffusion compressor stator blades. Data were taken at Reynolds numbers based on stator blade chord of 240000 and 711000. Total pressure measurements were first conducted upstream and downstream of the blades row. The approaching boundary layer was characterized and the downstream vortex locations were measured in detail. Upstream and downstream three-dimensional fibre-optic laser Doppler velocimetry surveys were conducted to measure the velocity profiles of the approaching boundary layer and to map the location and velocity characteristics of the downstream wake and vortex system. Results clearly show the effect that the overall secondary flow in the blade passages has on the location of the two oppositely rotating vortices.
Influence of Tip Clearance on the Inter Blade and Exit Flow Field of a Turbine Rotor Cascade
Authors: Govardhan M. , Venkatrayulu N. , Vishnubhotla V. S.
Published: February 2015

A detailed study of flow through the blade passage and downstream of a linear turbine cascade was carried out for four cases of tip clearance including zero clearance. Apart from inlet traverse, a total of eight stations were chosen for inter-blade flow traversing between 5% and 95% of axial chord from leading edge. Downstream flow surveys were made at distances of 106% of axial chord from the blade leading edge. Pitchwise and spanwise traverses were conducted for each tip clearance at these stations using a small five hole probe. Provision was also made for the measurement of static pressure distribution on the suction and pressure surfaces and also on the blade tip surface when clearance is present.

At about 40% of axial chord from the leading edge, the presence of clearance vortex is identified inside the passage. The growth of the clearance vortex in size, its movement towards the suction surface and its increase in strength with the gap size were observed beyond 55% of axial chord till the trailing edge region. The rate of growth of the losses in the endwall region increased with clearance. Horse shoe vortex was not observed for the highest clearance. The overall losses increase rapidly with clearance in the rear half of the blade.
Numerical Calculation of Flow for Cascade With Tip Clearance
Authors: Mizuki Shimpei , Tsujita Hoshio
Published: February 2015

Three-dimensional incompressible turbulent flow within a linear turbine cascade with tip clearance is analyzed numerically. The governing equations involving the standard k-ε model are solved in the physical component tensor form with a boundary-fitted coordinate system. In the analysis, the blade tip geometry is treated accurately in order to predict the flow through the tip clearance in detail when the blades have large thicknesses. Although the number of grids employed in the present study is not enough because of the limitation of computer storage memory, the computed results show good agreements with the experimental results. Moreover, the results clearly exhibit the locus of minimum pressure on the rear part of the pressure surface at the blade tip.
Numerical Simulation of 3D Viscous Flow in a Linear Compressor Cascade With Tip Clearance
Authors: Kang Shun , Hirsch Charles
Published: February 2015

A Navier-Stokes solver is applied to investigate the 3D viscous flow in a low speed linear compressor cascade with tip clearance at design and off-design conditions with two different meshes. The algebraic turbulence model of Baldwin-Lomax is used for closure. Relative motion between the blades and wall is simulated for one flow coefficient. Comparisons with experimental data, including flow structure, static and total pressures, velocity profiles, secondary flows and vorticity, are presented for the stationary wall case. It is shown that the code predicts well the flow structure observed in experiments and shows the details of the tip leakage flow and the leading edge horseshoe vortex.
Experimental Studies on Methane-Fuel Laboratory Scale Ram Combustor
Authors: Kinoshita Y. , Kitajima J. , Seki Y. , Tatara A.
Published: February 2015

The laboratory scale ram combustor test program has been investigating to obtain fundamental combustion characteristics of a ram combustor which operates from Mach 2.5 to 5 for the super/hypersonic transport propulsion system. In our previous study, combustion efficiency had been found poor, less than 70%, due to a low inlet air temperature and a high velocity at Mach 3 condition. To improve the low combustion efficiency a fuel zoning combustion concept was investigated by using a sub-scale combustor model first. Combustion efficiency more than 90% was achieved and the concept was found very effective. Then a laboratory scale ram combustor was fabricated and combustion tests were carried out mainly at the simulated condition of Mach 5. A vitiation technique was used to simulate a high temperature of 1263 K. The test results indicates that ignition, flame stability and combustion efficiency were not so significant but the NOx emissions are a critical problem for the ram combustor at Mach 5 condition.
Modeling of Start-Up Behavior of Combined Cycle HRSGs
Authors: Jolly Sanjeev , Gurevich Arkadiy , Pasha Akber
Published: February 2015

A thorough understanding of boiler performance during start-up is essential in the design and operation of Heat Recovery Steam Generators (HRSGs). It is during this time interval that the boiler may be subjected to maximum thermal and pressure gradients. Repeated exposure to corresponding stresses may lead to the fatigue failure of the material. Despite its importance, not enough work has been done on this topic. The main objective of this research is to analyze the performance characteristics of HRSG during start-up with the help of a mathematical model. The main characteristics of interest are the steam flow, steam pressure, steam temperature and water level in the drum. The behavior of these parameters is studied during start-up at the normal operating conditions at different positions of the diverter damper, the vents and the drains. Since the superheater and evaporator sections are exposed to maximum gas temperatures, only these two sections are considered in the analysis although the given methodology could be applied to include other sections as well. Finally, a practical application of the proposed model is discussed with the help of a numerical example.
Effect of Incidence on Secondary Flows in a Linear Turbine Cascade
Authors: Murty G. V. Ramana , Venkatrayulu N.
Published: February 2015

The effect of incidence on the generation and growth of secondary flows in a linear turbine cascade was studied in the present investigations using a Variable Density Cascade Tunnel at an exit Mach number of 0.43 and a Reynolds number of 8 × 105. The angles of incidence chosen were +15°, +50, 0°, −5° and −8.5°. The flow field was surveyed at five axial stations from cascade inlet to exit with a view to understanding the development of the secondary flow with the help of the variation of mass averaged total pressure loss coefficient and the contours of local loss coefficients in the pitch and spanwise directions. The total pressure loss coefficient and the net secondary loss coefficient have shown a steady growth along the cascade upto about 74 of the axial chord from the leading edge and thereafter rose very rapidly. The incidence is found to have an effect on the passage vortex and the loss cores due to the inlet boundary layer.
Development Requirements for an Advanced Gas Turbine System
Authors: Bannister R. L. , Cheruvu N. S. , Little D. A. , McQuiggan G.
Published: February 2015

In cooperation with U.S. Department of Energy’s Morgantown Energy Technology Center, a Westinghouse led team is working on the second part of an 8-year, Advanced Turbine Systems Program to develop the technology required to provide a significant increase in natural gas-fired combined cycle power generation plant efficiency.

This paper reports on the Westinghouse program to develop an innovative natural gas-fired advanced turbine cycle which, in combination with increased thing temperature, use of advanced materials, increased component efficiencies and reduced cooling air usage, has the potential of achieving a lower heating value plant efficiency in excess of 60%.
Ceramic Hybrid Bearings in Air-Cycle Machines
Authors: Burgmeier Lyman , Poursaba Matt
Published: February 2015

Extensive research in the field of ceramic rolling contact bearings has been conducted over the past several years. The results of this research indicate that silicon nitride may offer significant improvements in rolling fatigue life and a possible increase in operating temperature. AlliedSignal Aerospace Systems & Equipment (ASE) and the Air Force Item Management Engineering Branch at Tinker Air Force Base are conducting a development program under contract to ARPA to introduce ceramic hybrid bearings into existing F-15, F-111, and C-130 aircraft fleets in a near-term program involving retrofitting mature air-cycle machines with such bearings. The air-cycle machine (ACM) is a complex bearing application, operating at very high speeds (up to 100,000 rpm) and at high temperatures. In more severe military ACM applications, mean times between failures (MTBF’s) of 2000 and 3000 hours are common. The fleet would see an immediate benefit from improved bearing life.

This paper describes the analytical approach to evaluating and comparing ceramic to steel bearings, describes the laboratory test program to verify performance, and discusses the life-cycle cost improvement and the flight test program.
Spectral and Timeresolved Radiation Measurements in a Model Gas Turbine Combustor
Authors: Koch R. , Krebs W. , Jeckel R. , Ganz B. , Wittig S.
Published: February 2015

In the context of an extensive experimental investigation of the turbulent, reacting flow in a model gas turbine combustor, the radiation emitted by the confined three-dimensional turbulent propane/air diffusion-flame has been studied. The present study comprises for the first time spectral and time-resolved measurements of the radiative intensity at different axial locations including the reaction zone, the mixing zone and the exit of the model combustor. The radiation measurements are presented together with measurements and CFD-calculations characterizing the reacting flow field. This data set is well suited for the validation of CFD-calculations including radiative heat transfer and also for studying the interaction between turbulence and radiation.
Numerical Simulation of Combustor Flows on Parallel Computers: Practical Limitations and Practical Experience
Authors: Kurreck M. , Wittig S.
Published: February 2015

A parallelized finite-volume algorithm for the prediction of two- and three-dimensional turbulent flow problems is presented. For the parallelization, the domain decomposition method is applied. Three different procedures for coupling the subdomains and two iterative methods for solving the system of algebraic equations are outlined. As typical applications, the two-dimensional flow in a model combustor, the three-dimensional flow in an experimental combustor and a jet-mixing flow are predicted using the parallel algorithms on two different parallel computing systems (Parsytec GCel, SUN-workstation cluster). A workstation cluster is suitable for a small number of processors (1–16) only. In contrast to this, a transputer cluster of 448 processors can be used efficiently. The comparision of the CPU-times of the parallel and the vectorized version of the CFD code, running on a SNI S600/20 vector computer, shows, that current technology vector processors give the best performance. Since the performance of the individual parallel processor can be increased without difficulty, parallel processing has the potential to solve large problems which cannot be solved by current vector computers.
Development of a Lean-Premixed Two-Stage Annular Combustor for Gas Turbine Engines
Authors: Bahlmann Fred C. , Visser B. Martien
Published: February 2015

The development, from concept to hardware of a lean-premixed two-stage combustor for small gas turbine engines is presented. This Annular Low Emission Combustor (ALEC) is based on a patent of R.J. Mowill. Emission characteristics of several prototypes of this combustor under a variety of conditions are presented. It is shown that ultra-low NOx levels (< 10 ppm) can be reached with satisfactory CO levels (< 50 ppm).
Hot Gas Cleaning for Combined Cycle Based on Pressurized Coal Combustion
Authors: Gudenau H. W. , Hoberg H. , Mayerhofer A.
Published: February 2015

The aim of a project supported by the Minister of Science and Technology is the development of a process for gas cleaning at temperatures above 1573K. The simultaneous removal of particles and alkalis should be possible with this process. This hot gas cleaning ought to be integrated into an advanced combined cycle based on a pressurized slag tap furnace. The research concerning the development of a venturi scrubber with molten slag have been done at the Institute of Ferrous Metallurgy of the Technical University of Aachen.

Studies concerning the chemical and physical properties of slags are necessary to realize such a system for hot gas cleaning. This research must be followed by research concerning the influence of physical properties of slags such as viscosity or surface tension on the atomization of liquids. Furthermore, studies are necessary concerning the precipitation efficiency of a venturi scrubber with a liquid which has the same physical properties as slag.

This paper presents thermochemical calculations with regard to the absorption of gaseous alkalis by molten slag. Furthermore, it contains the investigations concerning the influence of alkali oxides on the viscosity of moltén slag.
Advantages of Air Conditioning and Supercharging an LM6000 Gas Turbine Inlet
Authors: Kolp Donald A. , Guidotti Harold A. , Flye William M.
Published: February 2015

Of all the external factors affecting a gas turbine, inlet pressure and temperature have the greatest impact on performance. The effect of inlet temperature variations is especially pronounced in the new generation of high-efficiency gas turbines typified by the 40 MW GE LM6000. A reduction of 50 F (28 C) in inlet temperature can result in a 30% increase in power and a 4.5% improvement in heat rate. An elevation increase to 5000 feet (1524 meters) above sea level decreases turbine output 17%; conversely supercharging can increase output more than 20%.

This paper addresses various means of heating, cooling and supercharging LM6000 inlet air. An economic model is developed and sample cases are cited to illustrate the optimization of gas turbine inlet systems, taking into account site conditions, incremental equipment cost and subsequent performance enhancement.
Unsteady Boundary Layers on a Flat Plate Disturbed by Periodic Wakes: Part I — Measurement of Wake-Affected Heat Transfer and Wake-Induced Transition Model
Authors: Funazaki K.
Published: February 2015

Measurements of wake-affected heat transfer distributions on a flat plate are made by use of a wake generator that consists of a rotating disk and several types of circular cylinders. The main purpose of this study is to construct a wake-induced transition model in terms of an intermittency factor, considering the evolution of the wake-induced turbulent region, a so-called turbulent patch in a distance-time diagram. A comparison between the proposed transition model and the measured heat transfer data reveals that the transition model yields good agreement with the measured data of all test conditions in this study.
Aerodynamic Behavior of Asymmetric Jets in 3-D Furnaces
Authors: El-Mahallawy F. M. , Hassan M. A. , Ismail M. A. , Zafan H.
Published: February 2015

The purpose of this paper is to present and evaluate numerical experiments illustrating the flow features in a 3-D furnace utilizing unconventional asymmetrical jet that creates natural recirculation zone. The numerical simulation of this aerodynamic stabilization method have unveiled the three-dimensional nature of the flow pattern which possesses a quite large reverse flow region. The size and strength of the built recirculation zone would be capable of stabilizing the burning of low-quality fuels.
Water Injected LM 1600 Installation and Operating Experience
Authors: Robinson Thomas
Published: February 2015

In 1992 Alberta Natural Gas Company Ltd (“ANG”) installed a General Electric LM 1600 gas turbine at its Moyie compressor station in southeastern BC, Canada. The unit was packaged by Dresser Rand with a General Electric supplied power turbine. To comply with provincial emissions permitting requirements, and in response to growing environmental concerns, the gas turbine was installed with water injection for exhaust stack NOx control. Water was obtained from an underground well and, after treatment to bring the water to a condition specified by General Electric, was injected into the combustion chamber of the gas turbine. After commissioning, extensive on-site testing was conducted to determine the emissions from the unit using three different techniques, at a variety of load and water injection rates. These tests showed that the expected emission reductions had been achieved and allowed the optimum water injection flow rate to be accurately established for a range of operating conditions.
Measurements of the Tip Clearance Flow for a High Reynolds Number Axial-Flow Rotor: Part 1 — Flow Visualization
Authors: Zierke W. C. , Farrell K. J. , Straka W. A.
Published: February 2015

A high Reynolds number pump (HIREP) facility has been used to acquire flow measurements in the rotor blade tip clearance region-with blade chord Reynolds numbers of 3,900,000 and 5,500,000. The initial experiment involved rotor blades with varying tip clearances, while a second experiment involved a more detailed investigation of a rotor blade row with a single tip clearance. This paper focuses on flow visualization, employing techniques unique for use in water. The flow visualization on the blade surface and within the flow field indicate that the combination of centripetal acceleration and separation near the trailing edge of the rotor blade suction surface results in the formation of a trailing-edge separation vortex-a vortex which migrates radially upwards along the trailing edge and then turns in the circumferential direction near the casing, moving in the opposite direction of blade rotation. Flow visualization also helps in establishing the trajectory of the tip leakage vortex core. The trailing-edge separation vortex, which lies closer to the endwall than the tip leakage vortex, seems to have an influence on this trajectory. Finally, the periodic interaction of the rotor blades with wakes from the upstream inlet guide vanes-as well as freestream turbulence and vortex structure instabilities-affects the unsteadiness of the vortex.