bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas Turbine Mach Number Control With Simplified Fuel System
Authors: Dadd Graham J. , Chan Kin K.
Published: August 2014

The compressor exit Mach number control theory presented here will enable improved control of transient compressor working point trajectories of a turbine engine. This will allow the steady working line to be raised towards the surge boundary with the advantage of increased thrust and reduced specific fuel consumption. This new control method can replace the rigid acceleration and deceleration limiters of the fuel control loop, and achieve superior surge avoidance performance.

This paper documents the theoretical and practical study of Mach number controllers designed for implementation with a simplified fuel pump system and the subsequent testing of the controllers on an aero-engine in the sea level test bed in DERA Pyestock.

The new controller incorporated two Mach number dynamic limiting control loops (one each for acceleration and deceleration) besides the NH controller. Several designs were tested successfully and demonstrated not only Mach number control from idle to full power, but also surge avoidance. Engine start control was also tested in the latest engine test.
Evaluation of an Uncooled Focal Plane Array Infrared Camera for Effusion Cooling Research
Authors: McGhee Scott K. , Birk A. M.
Published: August 2014

This study assessed a low-cost, uncooled ferroelectric detector infrared camera for effusion cooling research. Advances in uncooled IR technology have led to applications previously limited to research-grade cameras. The imager operated in the 7–14μm waveband and sampled up to 30 frames per second. Thermal images were made of a matte-black flat plate, downstream of two cylindrical jets with injection angles of α = 30° and 90°, and L/D = 6. Thermocouple calibration was specific to each image. Statistical analysis and image analysis yielded detailed temperature maps with uncertainty as small as 0.9°C, a spatial resolution of 0.4mm, and a sensitivity of 0.1 °C. The system compared favorably with established infrared systems. Advantages include minimal instrumentation, on-line results, and a high degree of accuracy and resolution, at significantly reduced cost.
A Fiber-Optic Tip-Shroud Deflection Measurement System
Authors: Rooth Rudy A. , Hiemstra Wiebren
Published: August 2014

A dutch utility faced the fact that a second stage set of turbine blades of a gas turbine had to be replaced long before the estimated lifetime as a result of tip shroud deflection. This deflection caused the risk of loss of support between the individual tip shroud segments. The goal is to find the cause of the problem, to see how it increases with time and to take appropriate action to prevent the problem from occurring again.

A fiber-optic tip-shroud deflection monitor has been developed and tested on a gas turbine (Davinson, 1987) to study this phenomenon in real time.. The optical system is based on astigmatism to derive distance information from the measured optical signals. Characteristic features from the system are the good spatial resolution of about 1 millimeter, the distance resolution of about 0.1 millimeter and the distance from the probe tip to the target of about 20 millimeter. These specifications are difficult to achieve with for example capacitive sensors. The probe tip can withstand temperatures of about 500 °C. The system can be calibrated in situ, given a stable operation of the gas turbine. This is accomplished by stepping the probe tip over some distance and recording the signals corresponding to a certain point on the tip shroud. The instrument has been used to monitor the tip-shroud deflection in a gas turbine at various loads and over a time span of several months. The results indicate that the deflection can be divided in a part depending on the load and a part that is a permanent deflection. Based on the results, it can be judged whether blades need to be rejected because of a too large deflection.
Application of On-Line Optimization Technology to Plant Operation
Authors: Gay Rodney R.
Published: August 2014

Traditionally optimization has been thought of as a technology to set power plant controllable parameters (i.e. gas turbine power levels, duct burner fuel flows, auxiliary boiler fuel flows or bypass/letdown flows) so as to maximize plant operations. However, there are additional applications of optimizer technology that may be even more beneficial than simply finding the best control settings for current operation. Most smaller, simpler power plants (such as a single gas turbine in combined cycle operation) perceive little need for on-line optimization, but in fact could benefit significantly from the application of optimizer technology.

An optimizer must contain a mathematical model of the power plant performance and of the economic revenue and cost streams associated with the plant. This model can be exercised in the “what-if” mode to supply valuable on-line information to the plant operators. The following quantities can be calculated:

Target Heat Rate

Correction of Current Plant Operation to Guarantee Conditions

Current Power Generation Capacity (Availability)

Average Cost of a Megawatt Produced

Cost of Last Megawatt

Cost of Process Steam Produced

Cost of Last Pound of Process Steam

Heat Rate Increment Due to Load Change

Prediction of Future Power Generation Capability (24 Hour Prediction)

Prediction of Future Fuel Consumption (24 Hour Prediction)

Impact of Equipment Operational Constraints

Impact of Maintenance Actions

Plant Budget Analysis

Comparison of Various Operational Strategies Over Time

Evaluation of Plant Upgrades

The paper describes examples of optimizer applications other than the on-line computation of control setting that have provided benefit to plant operators. Actual plant data will be used to illustrate the examples.
Design, Fabrication, and Testing of Ceramic Joints for High Temperature SiC/SiC Composites
Authors: Singh M. , Lara-Curzio Edgar
Published: August 2014

Various issues associated with the design and mechanical evaluation of joints of ceramic matrix composites are discussed. The specific case of an affordable, robust ceramic joining technology (ARCJoinT) to join silicon carbide (CG-Nicalon™) fiber-reinforced-chemically vapor infiltrated (CVI) silicon carbide matrix composites is addressed. Experimental results are presented for the time and temperature dependence of the shear strength of these joints in air up to 1200°C. From compression testing of double-notched joint specimens with a notch separation of 4 mm, it was found that the apparent shear strength of the joints decreased from 92 MPa at room temperature to 71 MPa at 1200°C. From shear stress-rupture testing in air at 1200°C it was found that the shear strength of the joints decreased rapidly with time from an initial shear strength of 71 MPa to 17.5 MPa after 14.3 hours. The implications of these results in relation to the expected long-term service life of these joints in applications at elevated temperatures are discussed.
Ceramic Gas-Turbine 2.5 MW Engine for Gas Industry Application in Russia
Authors: Soudarev A. V. , Souryaninov A. A. , Grishaev V. V. , Podgorets V. Ya. , Tikhoplav V. Yu. , Soudarev B. V.
Published: August 2014

Some important aspects of attacking the problem of development of a low-NOx high-temperature metal-ceramic 2.5 MW gas-turbine engine (GTE) for stationary application, in particular, gas industry of Russia are discussed in the paper. At present, to drive the natural gas blower for gas industry in Russia gas-turbine units (GTU) are mainly used.
A High-Temperature Catalytic Combustor With Starting Burner
Authors: Yoshida Yusaku , Oyakawa Kenshun , Aizawa Yukio , Kaya Hiroshi
Published: August 2014

A catalytic combustion system has high potential to achieve low NOx emission level. When this combustion system is applied to a gas turbine, the required combustor performance must be maintained over a wide range of operating conditions. These conditions range from cold starting to steady-state operation. Particularly during the initial stage of cold starting when the catalyst is not yet activated, the catalyst must be heated by some means.

This study proposes a new concept of a catalytic combustor with a direct heating system using vaporizing tube for starting burner in order to downsize the combustor and reduce the warm-up time during cold starts. The effectiveness of this concept is experimentally verified. Furthermore, NOx, CO, and HC emissions during startup can be reduced to a low level so as to achieve ultra-low pollution of the catalytic combustion over a wide range of operating conditions from cold start to steady-state operation.

This paper outlines the operation concept covering cold start, verification of the concept through the experiments with flame visualization in the combustor, spray characteristics, construction of the combustor, and combustion characteristics that show low pollution in various operating conditions of the catalytic combustor.
Experience of Environmental Update of Gas-Pumping Units
Authors: Vesely S. , Paryzek S. , Soudarev A. , Vinogradov E. , Zakharov Yu. , Scholz K.-H. , Zizow E.
Published: August 2014

Results of the environmental update of GT-750-6 (“Nevsky Zavod”, 6 MW), KWU VR-438 (“Siemens”, 10 MW), MS-3002 (“General Electric”, 10 MW) gas-turbine unit combustors were examined. On the basis of some specific features of design and operating process in the combustors, original engineering approaches of their update using a technique of localized air blow into the fire space extreme temperature zones were developed. The technique was demonstrated to be effective for a variety of combustors. Using the technique, one needs no considerable changes of the combustor design. The fuel system and gas turbine plant automatic control and governing systems remain virtually intact.
Ignition Delay Time Modulation as a Contribution to Thermo-Acoustic Instability in Sequential Combustion
Authors: Ni Alexander , Polifke Wolfgang , Joos Franz
Published: August 2014

Pressure pulsations due to combustion instabilities have been encountered in a premixed sequential gas turbine combustor. Measured noise spectra display one or several distinct peaks at Strouhal numbers significantly larger than unity. Height and location of the peaks depend in a sensitve manner on fuel type and/or operating conditions.

The paper identifies a possible mechanism of the observed combustion instability and presents a mathematical model of acoustic self-excitation. The mechanism of self-excitation comprises interactions between the acoustic field in the fuel injector / burner with the ignition delay time of the fuel-air mixture and the heat release intensity:

• pressure drop in the fuel injector nozzle changes with variations of the acoustic pressure in the burner,

• variations of pressure drop and air flow velocity modulate the fuel concentration,

• acoustic perturbations in the pre-flame region influence the delay time for self-ignition and consequently lead to fluctuations of flame velocity and -position.

• fluctuations of flame velocity influence the refracation of acoustic waves at the flame front.

• fuel inhomogeneities modulate the heat release rate and consequently the rate of volume production by the flame.

Based on this structure of a self-excitation mechanism, an analytical model has been developed and used to compute eigenfrequencies and growth rates of instabilities. Some characteristics of the suggested self-excitated instabilities as they are predicted by the model match well with empirical information.
Computational Modelling of Self-Excited Combustion Instabilities
Authors: Brookes Steve J. , Cant R. Stewart , Dupere Iain D. J. , Dowling Ann P.
Published: August 2014

It is well known that lean premixed combustion systems potentially offer better emissions performance than conventional non-premixed designs. However, premixed combustion systems are more susceptible to combustion instabilities than non-premixed systems. Combustion instabilities (large-scale oscillations in heat release and pressure) have a deleterious effect on equipment, and also tend to decrease combustion efficiency. Designing out combustion instabilities is a difficult process and, particularly if many large-scale experiments are required, also very costly. Computational fluid dynamics (CFD) is now an established design tool in many areas of gas turbine design. However, its accuracy in the prediction of combustion instabilities is not yet proven.

Unsteady heat release will generally be coupled to unsteady flow conditions within the combustor. In principle, computational fluid dynamics should be capable of modelling this coupled process. The present work assesses the ability of CFD to model self-excited combustion instabilities occurring within a model combustor. The accuracy of CFD in predicting both the onset and the nature of the instability is reported.
Dual Fuel Dry Low Emissions (DLE) Combustion System for the ABB Alstom Power 13,4 MW Cyclone Gas Turbine
Authors: Alkabie H. , McMillan R. , Noden R. , Morris C.
Published: August 2014

In response to stringent environmental legislation and customer demands for improved thermal efficiency, ABB ALSTOM POWER UK Ltd has introduced the 13.4MW Cyclone gas turbine engine. In this machine higher efficiency is achieved by increased firing temperature and pressure ratio. In order to meet the environmental considerations the Cyclone is supplied with Dual Fuel DLE combustion system as standard. Successful operation of the combustion system required a careful balance between the component life and low emissions performance. The combustor performance specification included targets for the following parameters:-

• Low emissions, NOx, CO, UHC and smoke, on both gaseous and liquid fuels without water or steam injection

• Good turn down ratio

• Controlled combustor outlet temperature profiles, both OTDF and RTDF

• Low dynamic pressure fluctuations

• Reliable ignition and fuel change over on both gas and liquid.

• Reliable transient response

This paper describes the design and validation work undertaken in order to achieve these challenging targets. It is shown that these targets are not only achieved but in some cases exceeded resulting in an economical and environmentally sound combustion system.
An Examination of the Relationship Between Chemiluminescent Light Emissions and Heat Release Rate Under Non-Adiabatic Conditions
Authors: Haber Ludwig C. , Vandsburger Uri , Saunders William R. , Khanna Vivek K.
Published: August 2014

As combustion instability research has matured over the last decade the need for more detailed diagnostics has increased. One main gap in the diagnostics is the ability to obtain a reliable quantitative measure of unsteady heat release. In an effort to move in this direction using chemiluminescence as the measured quantity, this paper examines the formation of chemiluminescent light in the simple yet non-idealized environment of a Bunsen burner flame with co-flow of air. The results of the study show that OH* and CH* chemiluminescence can be modeled accurately using the simplified modeling approach outlined within the paper. The understanding of chemiluminescent light formation gained by the ability to model OH* and CH* light emissions accurately allows the correct interpretation of chemiluminescence in terms of heat release.
An Accurate and Affordable Spray Model for Gas Turbine Combustor Design
Authors: Tolpadi Anil K. , Aggarwal Suresh K. , Mongia Hukam C.
Published: August 2014

The mode of fuel preparation, the method of injection into a combustor and its atomization characteristics have a significant impact on emissions. A simple dilute spray model which assumes sequential droplet heating and vaporization has been implemented in the past within computational fluid dynamics (CFD) codes at GE and has been used extensively for combustion applications. This spray model coupled with an appropriate combustion model makes reasonable predictions of the combustor pattern factor and emissions. In order to improve upon this predictive ability, a more advanced quasi-steady droplet vaporization model has been considered. This approach that accounts for simultaneous droplet heating and vaporization, using an infinite-conductivity model, and is therefore more realistic has been described in an earlier paper (Tolpadi et al., 1999). In the present study, the droplet submodels used for the computation of droplets’ trajectories and vaporization histories have been improved. The transient liquid-phase transport is represented by the conduction-limit and effective-conductivity models, the drag coefficient correlation is modified to account for the effect of droplet vaporization, the variable thermophysical properties of both liquid and gas phases are considered, and the high-pressure effects are included. Validation of this new approach for a single droplet was initially performed. Subsequently, calculations of the flow and temperature field were conducted and emissions (NOx, CO and UHC) were predicted for a modern single annular turbofan engine combustor using all the aforementioned droplet modeling approaches.
Experimental and Numerical Investigation on the Evaporation of Shear-Driven Multi-Component Liquid Wall Films
Authors: Gerendas M. , Wittig S.
Published: August 2014

The presented work is concerned with two-phase flows similar to those in prefilming airblast atomizers and combustors employing film vaporization. Correlations for the multi-component mixture properties and models for the calculations of the multi-component evaporation were implemented in a well tested elliptic finite-volume code GAP-2D (Wittig et al., 1992) utilizing time-averaged quantities, k,ε-turbulence model, wall functions, and curve-linear coordinates in the gas phase, adiabatic or diabatic conditions at the film plate, partially turbulent velocity profile, uniform temperature and rapid mixing approach in the wavy film. This new code GAP-2K was tested for stability, precision, and grid independence of the results by applying it to a turbulent hot air flow over a two-component liquid film, a mixture of water and ethanol in different concentrations. Both simulations and experiments, were carried out over a wide range of inlet conditions, such as inlet pressure (1–2.6 bar), inlet temperature (298–573 K), inlet air velocity (30–120 m/s), initial liquid flow rate (0.3–1.2 cm2/s), and initial ethanol concentration (20–75 % mass). Profiles of temperature-, gas velocity, and concentration of the evaporating component normal to the film, and the development of the film temperature, the static pressure, the liquid flow rate and the liquid compound along the film plate have been measured and compared with the simulation showing a good match.
Control Optimization of the Transient Performance of the Selective Bleed Variable Cycle Engine During Mode Transition
Authors: Grönstedt U. T. J. , Pilidis P.
Published: August 2014

The transient performance of the Selective Bleed Variable Cycle Engine (VCE) has been optimized during the transition from subsonic to supersonic mode. The Selective Bleed VCE concept has been developed with a Short Take-Off Vertical Landing (STOVL) aircraft in mind and the engine is characterized by its twin mode VCE feature. The transition optimization is constrained by the requirement of maintaining thrust and compressor surge margins. The engine variable geometry component schedules and the fuel flow are used as optimization variables. A differential algebraic formulation of an inter-component volume model is used to model the transient behavior of the engine. Sequential Quadratic Programming (SQP) is applied to the non-linear transient engine model directly, in order to solve the multivariable control problem. It is predicted that the mode switch can be carried out safely without violating the constraints and that the time required is limited by the actuator time of the hydraulic system.
Gas Turbine Combined Cycle With CO2-Capture Using Auto-Thermal Reforming of Natural Gas
Authors: Andersen Thormod , Kvamsdal Hanne M. , Bolland Olav
Published: August 2014

A concept for capturing and sequestering CO2 from a natural gas fired combined cycle power plant is presented. The present approach is to decarbonise the fuel prior to combustion by reforming natural gas, producing a hydrogen-rich fuel. The reforming process consists of an air-blown pressurised auto-thermal reformer that produces a gas containing H2, CO and a small fraction of CH4 as combustible components. The gas is then led through a water gas shift reactor, where the equilibrium of CO and H2O is shifted towards CO2 and H2. The CO2 is then captured from the resulting gas by chemical absorption. The gas turbine of this system is then fed with a fuel gas containing approximately 50% H2. In order to achieve acceptable level of fuel-to-electricity conversion efficiency, this kind of process is attractive because of the possibility of process integration between the combined cycle and the reforming process.

A comparison is made between a “standard” combined cycle and the current process with CO2-removal. This study also comprise an investigation of using a lower pressure level in the reforming section than in the gas turbine combustor and the impact of reduced steam/carbon ratio in the main reformer. The impact on gas turbine operation because of massive air bleed and the use of a hydrogen rich fuel is discussed.
Aero-Thermodynamic Simulation of a Double-Shaft Industrial Evaporative Gas Turbine
Authors: Camporeale S. M. , Fortunato B.
Published: August 2014

A modeling study has been carried out in order to determine the behavior of evaporative industrial gas turbines power plants at part-load and for varying ambient temperature.

On-design and off-design performance have been analyzed by means of a computational program developed for the analysis of advanced cycles.

In order to verify the mathematical model and to evaluate the characteristics of up-to-date gas turbine technology, an industrial engine, presently available on the market, has been simulated. A double-shaft gas turbine for power generation has been considered. On-design performance and ratings vs. ambient temperature have been evaluated, with good accordance.

It is assumed that, in order to realize a Recuperated Water Injected (RWI) cycle, the industrial gas turbine could be modified, maintaining substantially unchanged the compression system and modifying the turbine blades.

The thermodynamic analysis of the cycle has been carried out in order to determine efficiency and power output as a function of the amount of water addition.

The RWI cycle gas turbine has been designed and the characteristic maps of the two new turbines have been evaluated.

The regulation is performed by means of the simultaneous manipulation of fuel flow rate, water rate, and position of the free turbine nozzle guide vanes (NGV). The regulation criteria, the interaction among the input variables, the safety of the operations (max. turbine inlet temperature, surge limits) and the optimization of the part-load efficiency, are examined and discussed.

Ratings as a function of the ambient temperature are examined. The possibility to manipulate the water rate and the position of the NGV in order to provide high efficiency and power output, even on hot days, has been examined.

The paper shows that maintaining constant the temperature at the power turbine exit, ratings decrease of 17% in power and 5% in efficiency.
Conceptual Design for Medium Size Combined Cycle Plants Improved by Recent Research and Innovation
Authors: Jericha H. , Neumayer F.
Published: August 2014

A conceptual design study for a 120 MW combined cycle plant is presented here. Values of 60% thermal efficiency are at present the realm of very large gas turbines of most advanced design with power outputs of 300 to 500 MW. For industry and district heating plants it would be of most economic value to achieve similar thermal efficiencies in medium size gas turbines and combined cycle plants as they are being installed in Central European cogeneration and district heating plants.

The authors propose by concerted application of recent research results to achieve this goal for medium size combined cycle plants. Design measures incorporated are transonic turbine stages, an innovative cooling system and a 600 degree reheat steam turbine.
Hot-Gas-Path Life Extension Options for the V94.2 Gas Turbine
Authors: Bohrenkämper Gerhard , Bals Herbert , Wrede Ursel , Umlauft René
Published: August 2014

Gas turbine and combined cycle power plants are typically designed for a service life of over 30 years. If operated at base load in continuous duty, the gas turbine hot-gas-path components for example in a combined-cycle power plant need repair and replacement according to the maintenance program several times during plant life. Most of the hot components would reach the end of their service life, e.g. 100,000 equivalent operating hours (EOH), after 10 to 12 years. As this is well before the end of the overall plant service life defined in the power plant concept, such plant applications therefore necessitate life extension measures enabling to continuing operation beyond 100,000 EOH. This paper presents strategic options for hot-gas-path component life entension.
Manufacturers’ Role in the Power Industry
Authors: Mukherjee Dilip K.
Published: August 2014

This paper discusses the transformation which the power industry is presently undergoing and its impact on manufacturers’ business. The key success factors for a Manufacturer in today’s market are:

• Global market coverage with local customer services

• Broad portfolio of products and solutions

• Economy of scale and cost efficiency

• Substantial R&D resources for the technology race

Significant challenges exist for the manufacturers to fulfil the requirements, especially those relating to the proper organisational set-up, the right product and the required R&D program.
Leakage Flow Over Shrouded Turbine Blades
Authors: Xiao Yumin , Amano R. S.
Published: August 2014

In this paper the flows over shrouded turbine blades with single, double, and triple tip seals were simulated by using the two-dimensional Reynolds-averaged Navier-Stokes equations and a compressible k-ε turbulence model. A multi-zone technique was used to generate the grids in the complex flow channel. The calculation results showed that the flow in the seal channel is very complicated and the leakage flow rate is dominated by the minimum flow area and the pressure difference. It showed that the leakage flow rate varies as a function of the number of seals to the power of −0.45. For the cases of multiple-seals the space between two seals has little effect on the total mass flow rate. Finally, it appears there is not a simple function between the leakage flow and the pressure difference.
Heat Transfer and Flow on the Squealer Tip of a Gas Turbine Blade
Authors: Azad Gm S. , Han Je-Chin , Boyle Robert J.
Published: August 2014

Experimental investigations are performed to measure the detailed heat transfer coefficient and static pressure distributions on the squealer tip of a gas turbine blade in a five-bladed stationary linear cascade. The blade is a 2-dimensional model of a modern first stage gas turbine rotor blade with a blade tip profile of a GE-E3 aircraft gas turbine engine rotor blade. A squealer (recessed) tip with a 3.77% recess is considered here. The data on the squealer tip are also compared with a flat tip case. All measurements are made at three different tip gap clearances of about 1%, 1.5%, and 2.5% of the blade span. Two different turbulence intensities of 6.1% and 9.7% at the cascade inlet are also considered for heat transfer measurements. Static pressure measurements are made in the mid-span and near-tip regions, as well as on the shroud surface opposite to the blade tip surface. The flow condition in the test cascade corresponds to an overall pressure ratio of 1.32 and an exit Reynolds number based on the axial chord of 1.1×106. A transient liquid crystal technique is used to measure the heat transfer coefficients. Results show that the heat transfer coefficient on the cavity surface and rim increases with an increase in tip clearance. The heat transfer coefficient on the rim is higher than the cavity surface. The cavity surface has a higher heat transfer coefficient near the leading edge region than the trailing edge region. The heat transfer coefficient on the pressure side rim and trailing edge region is higher at a higher turbulence intensity level of 9.7% over 6.1% case. However, no significant difference in local heat transfer coefficient is observed inside the cavity and the suction side rim for the two turbulence intensities. The squealer tip blade provides a lower overall heat transfer coefficient when compared to the flat tip blade.
Influence of Surface Roughness on Heat Transfer and Effectiveness for a Fully Film Cooled Nozzle Guide Vane Measured by Wide Band Liquid Crystals and Direct Heat Flux Gauges
Authors: Guo S. M. , Lai C. C. , Jones T. V. , Oldfield M. L. G. , Lock G. D. , Rawlinson A. J.
Published: August 2014

The influence of surface roughness on heat transfer coefficient and cooling effectiveness for a fully film cooled 3D nozzle guide vane (NGV) has been measured in a transonic annular cascade using wide band liquid crystal and direct heat flux gauges (DHFGs). The liquid crystal methods were used for rough surface measurements and the DHFGs were used for the smooth surfaces. The measurements have been made at engine representative Mach and Reynolds numbers and inlet freestream turbulence intensity. The aerodynamic and thermodynamic characteristics of the coolant flow have been modelled to represent engine conditions by using a heavy “foreign gas” (30.2% SF6 and 69.8% Ar by weight). Two cooling geometries (cylindrical and fan-shaped holes) have been tested. The strategies of obtaining accurate heat transfer data using a variety of transient heat transfer measurement techniques under the extreme conditions of transonic flow and high heat transfer coefficient are presented.

The surfaces of interest are coated with wide-band thermochromic liquid crystals which cover the range of NGV surface temperature variation encountered in the test. The liquid crystal has a natural peak-to-peak roughness height of 25 μm creating a transitionally rough surface on the NGV. The time variation of colour is processed to give distributions of both heat transfer coefficient and film cooling effectiveness over the NGV surface. The NGV was first instrumented with the DHFGs and smooth surface tests preformed. Subsequently the surface was coated with liquid crystals for the rough surface tests. The DHFGs were then employed as the means of calibrating the liquid crystal layer. The roughness of 25 μm, which is the typical order of roughness for the in service turbine blades and vanes, increases the heat transfer coefficient by up to 50% over the smooth surface level. The film cooling effectiveness is influenced less by the roughness.
Rotor / Stator Heat Transfer Measurements and CFD Predictions for Short-Duration Turbine Rig Tests
Authors: Bergholz Robert F. , Dunn Michael G. , Steuber Gary D.
Published: August 2014

This paper describes aerodynamic and heat transfer measurements, improved data analysis techniques, and CFD predictions for an extensive series of high-pressure turbine tests carried out in a large-scale, short-duration test facility. The focus of this work is on the test methods, aerodynamic and heat transfer instrumentation, and the heat flux data obtained on the HPT blade and vane pressure and suction surfaces, and on the blade platform. Heat transfer data are presented along three spanwise stream surfaces, and at five platform locations, for two Reynolds numbers, and for three different initial blade temperature levels. An analytical method for improving the interpretation of transient heat flux gage measurements and estimating the uncertainties in heat transfer coefficients is applied based on test facility characteristics, established 2D boundary layer heat transfer theory, and a detailed calculation of the transient temperature response of the heat flux gages as installed in the airfoils. The result is a systematic procedure for improved data reduction and correction of bias errors resulting from in-situ heat flux gage behavior in complex rotating rig tests. Three-dimensional aerodynamic calculations are compared with time-averaged unsteady pressure measurements on the airfoils. Boundary-layer heat transfer predictions are shown to be in fair agreement with the pitchline data but sensitive to assumptions regarding free-stream turbulence, uncertainties in inlet conditions, and variations in the applied surface Mach number distribution. Finally, full 3D heat transfer computations for the blade are discussed, with an emphasis on capturing overall 3D flow effects with sufficient accuracy for practical turbine airfoil cooling design. The results suggest that advanced analysis techniques, including 3D CFD, can be used effectively to compute not only mean values of the surface heat transfer coefficients, but also to quantify the uncertainties in the predictions and to identify the dominant sources of those uncertainties. This is an important step in creating a robust turbine cooling design process that accounts for environmental, manufacturing, and modeling variations.

Future papers will present experimental and computational results for the blade tip and shroud, the vane endwalls, and TBC-coated airfoils.
Comparison of Predicted and Measured Turbine Vane Rough Surface Heat Transfer
Authors: Boyle R. J. , Spuckler C. M. , Lucci B. L.
Published: August 2014

Predicted turbine vane heat transfer for a rough surface over a wide range of test conditions was compared with experimental data. Inlet pressures varied between 0.2 and 1 atm., and exit Mach numbers ranged between 0.3 and 0.9. Thus, while a single rough surface vane was used for the tests, the effective roughness in wall units varied by more than a factor of ten. Comparisons were made for both high and low freestream turbulence intensities. Two-dimensional Navier-Stokes heat transfer predictions were obtained using the code RVCQ3D. Results were obtained using both algebraic and k–ω turbulence models. The algebraic model incorporated the Cebeci-Chang roughness model. The k–ω turbulence model accounts for roughness in the boundary condition. Roughness causes turbulent flow over the vane surface. Even after accounting for transition, surface roughness significantly increased heat transfer compared to a smooth surface. The k–ω results agreed better with the data than the Cebeci-Chang model. The low Reynolds number k–ω model did not accurately account for roughness at low freestream turbulence levels. The high Reynolds number version of this model was more suitable at low freestream turbulence levels.
Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 2 — Detailed Measurements
Authors: Nikitopoulos D. E. , Eliades V. , Acharya S.
Published: August 2014

Detailed heat/mass transfer distributions are presented inside a two-pass rotating ribbed coolant channel for two profiled-rib configurations. Several profiled-rib configurations have been studied (Acharya et al.; 2000), and it was found that the best performance was achieved by saw-tooth ribs, and a pyramid–valley rib combination. The profiled ribs were placed directly opposite to each other on the leading and trailing surfaces. Smooth side walls were used in all the experiments. Heat transfer measurements were compared with straight ribs of equal blockage ratio. The measurements were made in a two-pass rotating facility using the naphthalene sublimation mass transfer technique which provides highly resolved surface distributions. The results presented are for a Reynolds number of 30,000 two Rotation numbers (0 and 0.3) and include average heat/mass transfer over the entire inter-rib-module as well as detailed heat/mass transfer contours for two profiled-rib cases. Significant enhancements of up to 25% in heat/mass transfer was obtained with the pyramid-valley, and saw-tooth shaped ribs under rotating conditions.
Aerodynamic Loss Characteristics of a Turbine Blade With Trailing Edge Coolant Ejection: Part 1 — Effect of Cut-Back Length, Spanwise Rib Spacing, Free Stream Reynolds Number and Chordwise Rib Length on Discharge Coefficients
Authors: Uzol Oğuz , Camcı Cengiz , Glezer Boris
Published: August 2014

The internal fluid mechanics losses generated between the blade plenum chamber and a reference point located just downstream of the trailing edge are investigated for a turbine blade trailing edge cooling system. The discharge coefficient Cd is presented as a function of the free stream Reynolds number, cut-back length, spanwise rib spacing and chordwise rib length. The results are presented in a wide range of coolant to free stream mass flow rate ratios. The losses from the cooling system show strong free stream Reynolds number dependency especially at low ejection rates when they are correlated against the coolant to free stream pressure ratio. However, when Cd is correlated against a coolant to free stream mass flow rate ratio, the Reynolds number dependency is eliminated. The current data clearly shows that internal viscous losses due to varying rib lengths do not differ significantly. The interaction of the external wall jet in the cut-back region with the free stream fluid is also a strong contributor to the losses. Since the discharge coefficients do not have Reynolds number dependency at high ejection rates, Cd experiments can be performed at a low free stream Reynolds number. Running a discharge coefficient experiment at low Reynolds number (or even in still air) will sufficiently define the high blowing rate portion of the curve. This approach is extremely time efficient and economical in finding worst possible Cd value for a given trailing edge coolant system.
Natural Transition Phenomena on an Axial Compressor Blade
Authors: Hughes J. D. , Walker G. J.
Published: August 2014

Data from a surface hot-film array on the outlet stator of a 1.5 stage axial compressor are analyzed to look for direct evidence of natural transition phenomena. An algorithm is developed to identify instability waves within the Tollmien Schlichting (T-S) frequency range. The algorithm is combined with a turbulent intermittency detection routine to produce space∼time diagrams showing the probability of instability wave occurrence prior to regions of turbulent flow. The paper compares these plots for a range of blade loading, with free-stream conditions corresponding to the maximum and minimum inflow disturbance periodicity produced by inlet guide vane clocking. Extensive regions of amplifying instability waves are identified in nearly all cases. The implications for transition prediction in decelerating flow regions on axial turbomachine blades are discussed.
Effects of Turbulence and Solidity on the Boundary Layer Development in a Low Pressure Turbine
Authors: Solomon W. J.
Published: August 2014

Multiple-element surface hot-film instrumentation has been used to investigate boundary layer development in the 2 stage Low Speed Research Turbine (LSRT). Measurements from instrumentation located along the suction surface of the second stage nozzle at mid-span are presented. These results contrast the unsteady, wake-induced boundary layer transition behaviour for various turbine configurations.

The boundary layer development on two new turbine blading configurations with identical design vector diagrams but substantially different loading levels are compared with a previously published result. For the conventional loading (Zweifel coefficient) designs, the boundary layer transition occurred without laminar separation. At reduced solidity, wake-induced transition started upstream of a laminar separation line and an intermittent separation bubble developed between the wake-influenced areas.

A turbulence grid was installed upstream of the LSRT turbine inlet to increase the turbulence level from about 1% for clean-inlet to about 5% with the grid. The effect of turbulence on the transition onset location was smaller for the reduced solidity design than the baseline. At the high turbulence level, the amplitude of the streamwise fluctuation of the wake-induced transition onset point was reduced considerably. By clocking the first stage nozzle row relative to the second, the alignment of the wake-street from the first stage nozzle with the suction surface of the second stage nozzle was varied. At particular wake clocking alignments, the periodicity of wake induced transition was almost completely eliminated.
Flow Visualisation in a Rotating Cavity With Axial Throughflow
Authors: Bohn Dieter E. , Deutsch Gregor N. , Simon Burkhard , Burkhardt Claus
Published: August 2014

Annular cavities are found inside rotor shafts of turbomachines with an axial or radial throughflow of cooling air. In order to increase efficiency and system reliability, flow and heat transfer phenomena in those cavities have to be investigated in order to minimize thermal load. For research purposes an experimental rig is set up.

This paper focuses on flow visualisation using a laser light sheet technique in a heated rotating cavity which is axially flown through by cooling air. Flow phenomena are observed by a rotating telemetric video camera which shows smoke flowing through the light sheet area located in the axial midplane. The visualisation procedure is described and the first results are pointed out. Additionally, heat transfer measurement across the wall is shown.
Film Cooling Jet Aerodynamics for a Pipe and a Converging Nozzle Injection Hole
Authors: Sasahara Jun , Suzuki Yukiko , Tanaka Shigeru , Shizawa Takaaki , Honami Shinji
Published: August 2014

This paper presents the experimental study of film cooling jet aerodynamics for a pipe and a converging nozzle injection hole. The pipe jet has a fully developed velocity profile, and the nozzle jet has a top-hat one at the exit of the injection hole. The film cooling jet is injected into a turbulent boundary layer on a flat plate with 30° inclination angle. The mass flux ratio of the cooling jet to the primary flow is set at 0.8 and 1.2. Three components of mean velocity, vorticity and turbulent kinetic energy are measured using an X-array hot wire anemometer. The kidney vortex from the pipe jet is located closer to the wall than those from the nozzle jet. A tab is also installed at the exit of an injection hole to prevent the primary flow from convoluting. The effect of tab on the pipe jet is explicit.
Systematic Experimental and Numerical Investigations on the Aerothermodynamics of a Film Cooled Turbine Cascade With Variation of the Cooling Hole Shape: Part II — Numerical Approach
Authors: Hildebrandt Thomas , Ganzert Wolfgang , Fottner Leonhard
Published: August 2014

An extensive numerical study was accomplished in order to accompany an experimental research program. The present work is focussed on the influence of the shape and the inclination of film cooling holes on the aerodynamic of the turbine cooling flow. Four different cooling hole geometries located on the suction side of a large scale turbine cascade were modelled and numerically simulated over the entire range of practically applicable blowing ratios. The thermodynamic conditions chosen, were in order to simulate comparable engine conditions.

Having computer limitations in mind, former simulations had to cope with either of two limitations. Meshing the entire domain led to an insufficient grid resolution in the vicinity of the ejection area, omitting valuable detailed flow information. In contrast, the so-called local approach (Vogel, 1996) overcame this problem by isolating an area close to the ejection zone, hence leading to a proper numerical resolution. A major drawback of this method is the required assumption for a limiting streamsurface, which often led to an inaccurate pressure distribution on the blade surface. Therefore, a new numerical technique in applying a 3D Navier-Stokes code on cooling flow problems — the global approach — was used, overcoming the restrictions of the above mentioned approaches. In the frame of these numerical investigations the commercially available CFD-package FINE™/Turbo by NUMECA was used.

The CFD-package incorporates a modern flow solver and the capability to perform multi-species computations, which was utilised herein. A second species (tracer gas) with the properties of air, was introduced, ejecting from the cooling plenum, hence strongly facilitating the visual detection of the emerging and dispersing cooling flow. The numerical resolution reached well over one million grid points.

The distributions of the tracer concentration and the oil and dye visualisations clearly reveal a strong dependency between the cooling hole shape and the efficiency of the film cooling. A considerable increase in the latter could be achieved, if non-cylindrical cooling hole geometries were used. The CFD simulations are in a very good agreement with the measurements (Ganzert, Hildebrandt and Fottner, 2000), clearly uncoveringvery detailed flow phenomena, which could also be detected in the experimental results. It was found out that the shape and the inclination angle of the cooling holes are of paramount importance to the distributing pattern of the cooling air and hence to the cooling efficiency.
Fog System Performance in Power Augmentation of Heavy Duty Power Generating Gas Turbines Model 7EA
Authors: Ingistov Steve
Published: August 2014

Ambient air temperature plays significant role in performance of a Gas Turbine. Frequently Gas Turbines in electrical power generation are single rotor and are directly coupled to the Electrical Generators. These machines normally operate 8,000 hours per calendar year under the 100% load. The control of the combustion air flow is achieved by modulating compressor Inlet Guide Vanes (IGV). The single shaft axial compressor consumes as a rule of thumb more than 50% of turbine useful expansion work. Axial compressor is high-volume, moderate discharge pressure machine. Its power demand to discharge ambient air to the turbine combustion system is very dependent on ambient conditions such as pressure, temperature and relative humidity. The optimization of the axial compressor aerodynamic loading under various ambient conditions is therefore mandatory. During the hot and humid summer days, especially from the noon time to 6:00 PM, the demand for the power is at its maximum.

This Paper describes selection, design and installation of the Inlet Air Cooling System. (IACS). The selected IACS is fine water mist, FOG. FOG System (FS) was selected because of its efficiency and because the clean water was available. FS incorporates Fog Generating Skid (FGS) and Fog Curtain (FC). FC is comprised of lateral lines with equally spaced. FOG Nozzles (FN). The FN is specially designed to generate individual “Fog Cones” that efficiently dissipate the water particles in the space. Fine water particles are atomized by incoming air in the Inlet Air (IA) duct. The homogenous mixture of FOG and IA is required to enhance the water mist particles evaporation process. In cases when the FS works in tandem with Evaporative Cooler (EC) most of the FOG particles are “injected” into the compressor suction. The injected FOG particles start to evaporate during the IA compression process. The water evaporation process simultaneously causes cooling of the IA being compressed. The result is reduced compression work and improved performance of GT.