bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study on Axial Skewing Effect of a Turbine Stator by 3-D Navier-Stokes Analysis
Authors: Chen Naixing , Zhou Qian , Huang Weiguang
Published: February 2015

The objective of the present paper is to investigate the axial skewing effect of a turbine stator blading on its aerodynamic characteristics systematically, to find the possibility for reducing the secondary losses by using axially skewed bladings and to understand better its flow physics in turbomachinery. In the present paper a typical turbine stator blading is applied as an example to generate a set of axially skewed bladings for systematical study and illustration of their differences of aerodynamics characteristics. The paper gives the procedure for generating different forward-skewed and backward-skewed blades with the same profile sections at the same radius and the numerical method used is also described briefly. The method is based on the 3-D time-marching finite volume Navier-Stokes solution and was developed by the Institute of Engineering Thermophysics, Chinese Academy of Sciences. The turbulence model proposed by Baldwin and Lomax is used here for predicting the effective viscosity. The calculated results and their comparisons are also given in the present paper. On the basis of the analysis it is shown that the appropriate use of skewed blades gives designers another possibility to control the flow in the blade channel. By adopting forward-skewed blades to replace the straight blades can be reduced the blade loading near the leading edge and in the central part of the span. It is also found that the pressure gradient at the endwall of forward-skewed blading yields the radial force that enables to avoid the boundary layer separation from the endwall. The axial skew of blade enables to restrain the strength of the secondary flow. Therefore, the total pressure loss can be reduced. An attention should be paid: if the skewed blade for stator is chosen to be used, the radial distribution of the outlet flow angle from stator vane is required to meet the optimal incidence satisfaction to the rotor blades. Otherwise, it results in the reduction of efficiency.
A Numerically Supported Investigation of the 3D Flow in Centrifugal Impellers: Part I — The Validation Base
Authors: Hirsch Ch. , Kang S. , Pointel G.
Published: February 2015

The three-dimensional flow in centrifugal impellers is investigated on the basis of a detailed analysis of the results of numerical simulations. In order to gain confidence in this process, an in-depth validation is performed, based on computations of Krain’s centrifugal compressor and of a radial pump impeller, both with vaneless diffusers. Detailed comparisons with available experimental data provide high confidence in the numerical tools and results. The appearance of a high loss ‘wake’ region results from the transport of boundary layer material from the blade surfaces to the shroud region and its location depends on the balance between secondary and tip leakage flows and is not necessarily connected to 3D boundary layer separation. Although the low momentum spots near the shroud can interfere with 3D separated regions, the main outcome of the present analysis is that these are two distinct phenomena. Part I of this paper focuses on the validation base of the numerical approach, based on fine mesh simulations, while Part II presents an analysis of the different contributions to the secondary flows and attempts to estimate their effect on the overall flow pattern.
Turbulent Flow Computations in Rotating Cavities Using Low-Reynolds-Number Models
Authors: Iacovides Hector , Nikas Kostas S. , Te Braak Marcel A. F.
Published: February 2015

This study is concerned with the use of low-Reynolds-number models of turbulence transport in the computation of flows through rotating cavities. The models tested are the Launder and Sharma low-Re k-ε (L-S) and a low-Re differential second-moment closure (DSM), first used by Iacovides and Toumpanakis, both with and without the Yap correction term to the dissipation rate equation. The cases examined include rotor-stator systems without throughflow, rotor-stator systems with radial outflow, contra-rotating disc systems without throughflow and also with radial outflow, co rotating discs with radial outflow and also rotor-stator systems with radial inflow. Earlier studies have shown that, when no throughflow or when radial outflow is involved, the L-S tends to over-estimate the size of the regions over which the boundary layers remain laminar, while the zonal k-ε/l-eqn model is unable to predict partially laminarized flows. A modification to the ε equation proposed here, which in regions of low turbulence reduces the dissipation rate when the fluid is in solid body rotation, provides a simple empirical way to significantly improve the L-S predictions of partially laminarized flows through rotating cavities, to acceptable levels. The DSM model used, in some cases led to some further predictive improvements and, for rotor-stator systems without throughflow, to a significant improvement in the predicted value of the moment coefficient. The Yap length scale correction term, while in most cases it has either a beneficial or a neutral effect on the flow predictions, in cases involving radial inflow it leads to poorer predictions. Models that do not rely on wall distance thus appear more likely to have a wider range of applicability.
How to Get Component Maps for Aircraft Gas Turbine Performance Calculations
Authors: Kurzke Joachim
Published: February 2015

Precise simulations of gas turbine performance cannot be done without component maps. In the early days of a new project one often has to use scaled maps of similar machines. Alternatively one can calculate the component partload characteristics provided that the many details needed for such an exercise are available. In a later stage often rig tests will be done to get detailed information about the behavior of the compressors respectively turbines.

Performance calculation programs usually require the map data in a specific format. To produce this format needs some preprocessing. Measured data cannot be used directly because they show a scatter and they are not evenly distributed over the range of interest. Due to limitations in the test equipment often there is lack of data for very low and very high speed.

With the help of a specialized drawing program available on a PC one can easily eliminate the scatter in the data and also inter- and extrapolate additional lines of constant corrected speed. Many graphs showing both the measured data and the lines passing through the data as a function of physically meaningful parameters allow to check whether the result makes sense or not. The extrapolation of compressor maps toward very low speed, as required for the calculation of starting, idle and windmilling performance calculations, is discussed in some detail.

Instead of true measured data one can use data read from maps published in open literature. The program is also an excellent tool for checking and extending component maps one has derived from sparse information about a gas turbine to be simulated.
Effect of Aspect Ratio on the Buoyancy Driven Reverse Flow Near the Leading Wall of Rotating Cooling Passages
Authors: Tekriwal Prabhat
Published: February 2015

The present work is concerned with the flow reversal phenomenon that is caused by the centrifugal buoyancy forces in the case of three-dimensional radially outward flow through rectangular ducts rotating in orthogonal mode. Due to the flow reversal, regions of zero to low fluid velocity (stagnation) are created near the leading wall and the heat transfer, consequently, is impaired causing concerns for the design engineers. Three duct cross-sections of the same hydraulic diameter but different aspect ratios (1:1, 2:1 and 3.33:1) have been examined in this numerical study for flows at different rotation numbers and different temperature ratios. The rotation number examined ranged from 0.08 to 0.35. For each rotation number the temperature ratio is increased until the flow reversal phenomenon is observed in the CFD predictions. For all the three ducts, computations have been carried out for Reynolds number equal to 80,000. The onset of the flow reversal near the leading wall and at the exit of the single-pass flow passage is studied with the buoyancy number variation.

As the aspect ratio is increased while keeping the duct hydraulic diameter fixed, the buoyancy number required to cause the onset of flow reversal decreases. Also, for each of the three ducts examined it has been found that the buoyancy number required for the predicted reverse flow to occur increases as the rotation number is increased.
Leading Edge Film Cooling: Computations and Experiments Including Density Effects
Authors: He Pingfan , Licu Dragos , Salcudean Martha , Gartshore Ian S.
Published: February 2015

The effect of varying coolant density on film cooling effectiveness for a turbine blade-model was numerically investigated and compared with experimental data. This model had a semi-circular leading edge with four rows of laterally-inclined film cooling orifices positioned symmetrically about the stagnation line. A curvilinear coordinate-based CFD code was developed and used for the numerical investigation. The code used a domain segmentation strategy in conjunction with general curvilinear grids to model the complex blade configuration. A multigrid method was used to accelerate the convergence rate. The time-averaged, variable-density, Navier-Stokes equations together with the energy or scalar equation were solved. Turbulence closure was attained by the standard k–ε model with a near-wall k model. Either air or CO2 was used as coolant in three cases of injection through single rows and alternatively staggered double raws of holes. Two different blowing rates were investigated in each case and compared with experimental data. The experimental results were obtained using a wind tunnel model, and the mass/heat analogy was used to determine the film cooling effectiveness. The higher density of the carbon dioxide coolant (approximately 1.5 times the density of air) in the isothermal mass injection experiments, was used to simulate the effects of injection of a colder air in the corresponding adiabatic heat transfer situation. Good agreement between calculated and measured film cooling effectiveness was found for low blowing ratio M ≤ 0.5 and the effect of density was not significant. At higher blowing ratio M > 1 the calculations consistently overpredict the measured values of film cooling effectiveness.
A Novel Technique for the Internal Blade Cooling
Authors: Glezer B. , Moon H. K. , O’Connell T.
Published: February 2015

Development of an adequate air cooling system for the thermally highly loaded leading edge and tip of the blade, that is cost effective and also relatively insensitive to manufacturing tolerances and operating environment continues to be one of the major challenges in advanced gas turbine design. Extensive studies on the convective (including impingement) and film cooling techniques produced remarkable progress in achieving a high cooling effectiveness level for turbine airfoils. However, in the case of turbine blades, application of these techniques has severe limitations. Highly effective impingement cooling needs to be combined with film discharge of the spent air to avoid a negative impact of crossflow on internal heat transfer and also provide additional thermal protection of the surface downstream of the discharge holes. Noticeable aerodynamic penalties, stress concentration and significant increase in manufacturing cost limit application of blade film cooling, particularly for moderately high operating temperatures.

Search for a highly effective robust design of internal airfoil cooling which can delay the use of film cooling resulted in the creation of a new technique which is described in this paper. This technique is based on generation of a swirling flow structure in the blade internal leading edge passage. Significant heat transfer augmentation can be achieved when the cooling air is delivered into the leading edge plenum tangentially to the inner concave surface. The best results can be obtained when the swirling flow is allowed to move radially, creating a three-dimensional screw-shaped flow in the plenum.

The presented results of the flow and heat transfer studies performed for the practical range of Reynolds numbers for the internal flow show that the leading edge screw-shaped cooling technique provides internal heat transfer rate comparable with impingement coupled with film discharge of the spent air, is more effective than impingement with cross flow and is almost five times higher than heat transfer in the smooth channel.
Modelling Turbulent Combustion in a Non-Adiabatic CO/H2 Flame Using Reaction Progress Variables
Authors: Kok Jim B. W. , Louis Jurgen J. J.
Published: February 2015

A model is presented for the turbulent combustion of CO/H2-air mixtures at gas turbine conditions. The model takes account of heat losses. The conversion of CO to CO2 and of H2 to H2O, as well as the non-equilibrium intermediate species concentrations are determined by two reaction progress variables and two other scalar variables. The initially available fuel concentration is expressed by a fuel mixing variable. The heat loss effect on the enthalpy is described by a scaled enthalpy variable. The modelled turbulent source terms in the transport equations for the scalar variables are discussed. Three cases of a turbulent CO/H2 diffusion flame with heat loss and chemical super-equilibrium of intermediate species are presented.
ATEC: The Aerodynamic Turbine Engine Code for the Analysis of Transient and Dynamic Gas Turbine Engine System Operations: Part 1 — Model Development
Authors: Garrard Doug
Published: February 2015

A new one-dimensional, time dependent aerothermodynamic mathematical model and computer simulation of the gas turbine engine has been developed. The Aerodynamic Turbine Engine Code (ATEC) simulates the operation of the gas turbine engine by solving conservation equations, expressed as one dimensional, time dependent Euler equations, with turbomachinery source terms. By incorporating both implicit and explicit equation solvers, transient simulations of the gas turbine engine can be conducted efficiently while maintaining the capability of simulating dynamic events such as compressor stall. ATEC can also be used to address dynamic events or steady-state processes to model both on- and off-design engine operation.
Assessment of Three Turbulence Models in a Compressor Rotor
Authors: Shabbir A. , Zhu J. , Celestina M.
Published: February 2015

A blind test case for a compressor rotor (ROTOR 37) was organized by the ASME/IGTI at its 1994 meeting in order to assess the predictive capabilities of the turbomachinery CFD tools. The results from the different CFD codes showed a wide scatter which in part is due to the differences in the turbulence models that were used. In order to systematically isolate the capabilities and limitations of the turbulence models, ROTOR 37 flow is computed from the same numerical platform with three different turbulence models. These include: the Baldwin-Lomax model, the standard k-ϵ model, and an improved version of this k-ϵ model. The results from the three models are compared with the experiment. We find that with increasing model complexity the results move closer to the experiment. Several sensitivity studies are carried out to bracket the uncertainty in the computations. These include the effect of: wall boundary conditions for the turbulence models; numerical accuracy of the turbulence solver; and the effect of the inlet boundary condition for turbulence.
Evaluation of the Effectiveness of a Metal Deactivator and Other Additives in Reducing Insolubles in Aviation Fuels
Authors: Jones E. Grant , Balster Walter J. , Balster Lori M.
Published: February 2015

Surface fouling in aircraft fuel lines resulting from autoxidation of aviation fuel leads to reduced efficiency as deposits collect on heat exchangers, nozzles, and servocontrols and may ultimately lead to system failure. Metal surfaces and trace quantities of metals dissolved in the fuel exacerbate the surface-fouling problem because they can catalyze free-radical initiation, thereby accelerating autoxidation. Additives and additive packages containing antioxidants, dispersants, and metal deactivators (MDA) have been shown to reduce insolubles in some fuels. Because of metal chelation and possible metal-surface passivation, MDA has been proposed as an additive component to be included in all fuels, even those without dissolved metals. The goal of the present study was to obtain fundamental information on the behavior of MDA under conditions where surface-passivation effects are minimal. Experiments have been conducted to 1) study the effects of adding MDA to fuels containing a significant concentration of dissolved metals (i.e., chelation) and to those containing minor concentrations of dissolved metals and 2) investigate interactions when MDA is used in conjunction with an antioxidant and a dispersant.

Simple fuel-line-fouling simulations with a single-pass tubular heat exchanger operated under near-isothermal conditions have been conducted to study the thermal behavior at 185°C of several neat and MDA-treated jet fuels as well as fuels treated with MDA plus other additives. Comparison of neat and treated fuels is based on several criteria: 1) dependence of autoxidation on stress duration, 2) dependence of surface deposition on stress duration, and 3) quantity of total insolubles (bulk filterables and surface deposits). Potential advantages and disadvantages of using MDA alone and in combination are discussed.
Coupled Lagrangian Monte Carlo PDF–CFD Computation of Gas Turbine Combustor Flowfields With Finite–Rate Chemistry
Authors: Tolpadi Anil K. , Hu Iris Z. , Correa Sanjay M. , Burrus David L.
Published: February 2015

A coupled Lagrangian Monte Carlo Probability Density Function (PDF)–Eulerian Computational Fluid Dynamics (CFD) technique is presented for calculating steady three–dimensional (3–D) turbulent reacting flow in a gas turbine combustor. PDF transport methods model turbulence–combustion interactions more accurately than conventional turbulence models with an assumed shape PDF. The PDF transport equation was solved using a Lagrangian particle tracking Monte Carlo (MC) method. The PDF modeled was over composition only. This MC module has been coupled with CONCERT, which is a fully elliptic 3–D body–fitted CFD code based on pressure correction techniques. In an earlier paper [Tolpadi et al, 1995], this computational approach was described but only fast chemistry calculations were presented in a typical aircraft engine combustor. In the present paper, reduced chemistry schemes were incorporated into the MC module that enabled the modeling of finite rate effects in gas turbine flames and therefore the prediction of CO and NOx emissions. With the inclusion of these finite rate effects, the gas temperatures obtained were also more realistic. Initially, a two scalar scheme was implemented that allowed validation against Raman data taken in a recirculating bluff body stabilized CO/H2/N2–air flame. Good agreement of the temperature and major species were obtained. Next, finite rate computations were performed in a single annular aircraft engine combustor by incorporating a simple three scalar reduced chemistry scheme for Jet A fuel. This three scalar scheme was an extension of the two scalar scheme for CO/H2/N2 fuel. The solutions obtained using the present approach were compared with those obtained using the fast chemistry PDF transport approach [Tolpadi et al, 1995] as well as the presumed shape PDF method. The calculated exhaust gas temperatures using the finite rate model showed the best agreement with measurements made by a thermocouple rake. In addition, the CO and NOx emission indices were also computed and compared with corresponding data.
Fluctuating Thermal Field in the Near Hole Region for Film Cooling Flows
Authors: Kohli Atul , Bogard David G.
Published: February 2015

The film cooling flow field is the result of a highly complex interaction between the film cooling jets and the mainstream, Understanding this interaction is important in order to explain the physical mechanisms involved in the rapid decrease of effectiveness which occurs close to the hole exit. Not surprisingly, it is this region which is not modeled satisfactorily with current film cooling models. This study uses a high frequency response temperature sensor which provides new information about the film cooling flow in terms of actual turbulence levels and probability density functions of the thermal field. Mean and rms temperature results are presented for 35° round holes at a momentum flux ratio of I = 0.16, at a density ratio of DR = 1.05. Probability density functions of the temperature indicate penetration of the mainstream into the coolant core, and ejection of coolant into the mainstream. Extreme excursions in the fluctuating temperature measurements suggests existence of strong intermittent flow structures responsible for dilution and dispersion of the coolant jets.
Managing Naval Gas Turbines Through a Memorandum of Understanding
Authors: Markus J. Albert , Glennie Andy M. G.
Published: February 2015

This paper describes how four European navies have been able to work together for over twenty years in order to support their marine Tyne, Olympus and Spey gas turbines, used for surface ship propulsion, through two internationally agreed Memoranda of Understanding (MOUs).

It shows how the MOUs came into existence, what their main aims are, how they are organised and how MOU business is conducted to achieve these aims.

The final part of the paper discusses the merits of the existing MOUs and presents an insight into how they, and other MOUs currently under discussion, may develop in the future.
Allison Model 501-KH Industrial Gas Turbine Engine
Authors: Porter Ronald P.
Published: February 2015

The 6 MW class Allison 501-KH gas turbine was introduced to the industrial power generation market in the mid-1980s as a low risk modification of the 501-KB engine. The aero-derivative and industrial background of the 501-KB engine is discussed along with the 501-KH product definition and product description. The results of the development, and production 501-KH engines are presented, including performance testing and customer operation. In addition, near term improvement plans for the 501-KH and a boosted version are outlined.
Transonic Film-Cooling Investigations: Effects of Hole Shapes and Orientations
Authors: Wittig S. , Schulz A. , Gritsch M. , Thole K. A.
Published: February 2015

The emphasis of the present study is to understand the effects of various flowfield and geometrical parameters in the nearfield region of a scaled-up film-cooling hole on a flat test plate. The effect of these different parameters on adiabatic wall effectivenesses, heat transfer coefficients, discharge coefficients and the near-hole velocity field will be addressed. The geometrical parameters of concern include several angles of inclination and rotation of a cylindrical film-cooling hole and two different hole shapes — a fanshaped hole and a laidback fanshaped hole. The fluid dynamic parameters include both the internal and external Mach number as well as the mainstream-to-coolant ratios of total temperature, velocity, mass flux, and momentum flux. In particular, the interaction of a film-cooling jet being injected into a transonic mainstream will be studied.

This paper includes a detailed description of the test rig design as well as the measuring techniques. Firstly, tests revealing the operability of the test rig will be discussed. Finally, an outlook of the comprehensive experimental and numerical program will be given.
The Effect of High Temperature Feedwater on the Performance of an Evaporative Cooler Installed in a Gas Turbine Combustion Air Inlet System
Authors: Johnson R. S.
Published: February 2015

Feedwater temperatures above the ambient air wet-bulb and dry-bulb temperatures can significantly reduce the effectiveness of an evaporative cooler. Using the standard evaporative cooler equation significantly underestimates the temperature of the air leaving the evaporative cooler. This, in turn, causes an over estimate of the available power of the gas turbine. This paper describes a procedure for use in estimating the impact of high temperature feedwater on evaporative cooler effectiveness.
Experimental Measurement and CFD Prediction of Heat Transfer to a Nozzle Guide Vane
Authors: Kirsten Trevor J. , Lippert Andreas M. , Snedden Glen C. , Smith Graham D. J.
Published: February 2015

The determination of aerothermal loading plays a vital role in any performance or structural investigation of turbine hot-end components during both the design and in-service phases. This investigation considers the measurement and prediction of heat transfer on a nozzle guide vane in a linear cascade. The experimental method is based on a transient approach and requires that the gas and blade have the correct temperature difference. In this study the transient technique is facilitated by maintaining a constant external gas flow in a closed circuit cascade facility and moving a cooled MACOR blade rapidly into the cascade, displacing an aluminium dummy blade. For a short period of time the correct temperature ratio exists between the gas and blade. It is during this period that the change in the thin-film resistance is measured, which is transformed to represent surface heat transfer. The experimental data is compared to an analytical prediction using an Euler code for the bulk flow solution and a boundary layer code for surface heat transfer. The boundary layer code includes the effects of turbulence in the boundary layer, and the transitional nature of the boundary layer flow is also captured. The accuracy associated with the levels of heat transfer is shown to be good for two exit Mach numbers, although some variation is evident towards the trailing edge of the suction surface. The laminar, transitional and turbulent regions of the boundary layer show good correspondence.
Experimental Contribution on the Significance and the Control by Transverse Injection of the Horseshoe Vortex
Authors: Georgiou D. P. , Papavasilopoulos V. A. , Alevisos M.
Published: February 2015

The present study addresses two aspects of the horseshoe vortex, namely its significance in the secondary flow in a turbine blade passage and the possibility of reducing its strength by an active flow mechanism, i.e the transverse injection of coolant air through a slot in a cylinder-endwall junction. The study reports on the results of two experiments in low speed wind tunnels, which employed a calibrated five-hole Pitot tube to measure the velocity vectors and the resulting secondary flowfields. The first aspect was studied in a 90° square cross section bend duct. The two horseshoe vortex legs were simulated by two half-Delta wing vortex generators. The results showed that the horseshoe vortices influence two regions of the secondary flowfield, i.e one near the passage entrance, where the pressure side leg forces a three dimensional separation of the endwall boundary layer, and the other is in the exit plane, where the coupling of the horseshoe with the passage vortex redistributes the flow with total pressure losses, without affecting the total loss, and increases the secondary kinetic energy by about 20%. For the second aspect, a rectangular bluff body, with a cylindrical leading edge, was positioned over the tunnel endwall and the transverse air injection was implemented through a thin slot, covering the 180° arc in the leading edge-endwall junction. The results showed that, for an average injection velocity equal to 35% that of the mainstream, the size and strength of the horseshoe vortex leg were reduced by nearly 60%. On the other hand, for stronger injection rates the vortex size and strength were increased.
The Effect of Impeller Inlet Annular Turning Vanes on Multistage Centrifugal Compressor Performance
Authors: Balligand Hélène , Huang Xiubao , Brasz Joost J.
Published: February 2015

The flow path of multistage centrifugal compressors is characterized by two 180-degree turns per stage: the inlet turning bend connecting the radial inflow return channel with the radial outflow impeller and the cross-over bend connecting the radial outflow diffuser with the return channel. Due to higher flow velocity and larger width to turning radius ratio, the turning losses are substantially higher in the inlet bend than in the return channel bend. Performance measurements were taken using different annular through-flow turning vane arrangements designed to reduce the inlet turning losses and increase the overall efficiency of the multistage centrifugal compressor. The experiments have shown consistent efficiency gains with corresponding capacity increases by adding multiple annular turning vanes in the inlet bend. The performance improvement potential of the vanes depends strongly on the positioning of these vanes in the flow passage. Based on these results, an empirical turning loss model was developed with the capability to predict the performance improvement achievable with correctly positioned single or multiple turning vanes in the impeller inlet bend area.
The Effect of Blade Angle Design Selection on Wave-Turbine Engine Performance
Authors: Lear William E. , Kielb Robert P.
Published: February 2015

Wave rotors have been investigated over several decades in part due to their potential for increasing the maximum cycle temperature in gas turbine engines via their self-cooling mechanism. Recent activities in this field have centered on the experiments and CFD design tools developed at NASA Lewis Research Center. Because of the fundamental objectives of that program, the work to date has concentrated on wave rotors rather than wave turbines. Wave turbines differ from wave rotors in that the flow passages are curved, similar to conventional turbines, so that the unit produces net shaft power. The purpose of this paper is to present an analysis technique which is used to quantify the substantial impact which blade curvature has on the maximum gas expansion ratio, and hence on the maximum cycle temperature. Limited optimization of the overall pressure ratio allows the maximum specific power and the corresponding efficiency to be found as a function of wave turbine inlet and exit blade angles and Mach number. A potential increase in specific power of 69% and a 6.8 percentage point increase in thermal efficiency over a conventional gas-turbine engine can be achieved through the use of a wave turbine.
A Parametric Study of the Flutter Stability Characteristics of Turbomachine Cascades
Authors: Försching H.
Published: February 2015

A parametric study of the unstalled flutter stability characteristics of compressor and turbine cascades in subsonic and supersonic flow is carried out. Based on typical section two-dimensional cascade models, stability boundaries and dominant trends in flutter behaviour are outlined with emphasis on the effects of (a) single mode structural coupling in bending and torsion, (b) coupling among multiple blade degrees of freedom, (c) mass ratio and structural damping, (d) compressibility, (e) cascade solidity and stagger, and (f) steady aerodynamic blade loading. Practical design aspects are in the foreground of all of these investigations.
Reliability Analysis of Power Generation Gas Turbine Auxiliaries Using Structured Analytical Methods
Authors: Rönnebeck Horst
Published: February 2015

For gas turbines used in power generation, reliability is one of the most important considerations. In the past, reliability was determined qualitatively (at best). When feedback from operation periods was available, reliability was recorded and rated statistically. However, in the present situation it is more and more necessary to quantify reliability quantities in the design stage of a new gas turbine (“built-in reliability”) with a sufficient accuracy.
European Standardisation Efforts on Fibre-Reinforced Ceramic Matrix Composites
Authors: Steen Marc
Published: February 2015

A critical phase in the life-cycle of a material is the transition from the development stage to that of design and industrial application. Advanced technical ceramics are currently in this phase and their future market penetration and acceptance as engineering materials critically depend on the availability of a robust set of standards for test methods which allow one to determine their mechanical and thermal properties in a reliable and reproducible way. In Europe, standardisation on continuous fibre reinforced ceramic matrix composites (CFCCs) officially started in 1989, when CEN TC 184 on Advanced Technical Ceramics was launched. The scope of TC 184 covers testing methods, and no efforts are paid to the development of material and product standards as yet. The work programme of TC 184 in the area of CFCCs, aimed at the establishment of testing methods for the generation of reliable data for design purposes, is reviewed.
The Effect of Thermal Aging on the Thermal Conductivity of Plasma Sprayed and EB-PVD Thermal Barrier Coatings
Authors: Dinwiddie Ralph B. , Beecher Stephen C. , Porter Wallace D. , Nagaraj Ben A.
Published: February 2015

Thermal barrier coatings (TBCs) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBCs is of primary importance. Electron beam-physical vapor deposition (EB-PVD) and air plasma spraying (APS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The density of the APS coatings was controlled by varying the spray parameters. The low density APS yttria-partially stabilized zirconia (yttria-PSZ) coatings yielded a thermal conductivity that is lower than both the high density APS coatings and the EB-PVD coatings. The thermal aging of both fully and partially stabilized zirconia are compared. The thermal conductivity of the coatings permanently increases upon exposure to high temperatures. These increases are attributed to microstructural changes within the coatings. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the EB-PVD coatings are less susceptible to thermal aging effects, results suggest that they typically have a higher thermal conductivity than APS coatings before thermal aging. The increases in thermal conductivity due to thermal aging for plasma sprayed partially stabilized zirconia have been found to be less than for plasma sprayed fully stabilized zirconia coatings.
The Effects of Environmental Contaminants on Industrial Gas Turbine Thermal Barrier Coatings
Authors: Eaton H. E. , Bornstein N. S. , DeMasi-Marcin J. T.
Published: February 2015

Thermal barrier coatings, (TBCs) play a crucial role in the performance of advanced aircraft gas turbine engines that power the commercial and military fleets. The same technology is currently being applied to the industrial gas turbines. However the task is more challenging. The environment of the industrial gas turbine is far more demanding. Studies are in progress delineating the relationships between time, temperature and the sinterability of candidate ceramics for use in industrial gas turbine engines. Typical sintering aids include the oxides and alkali salts of silicon, iron, magnesium and calcium. Other experiments focus on the role of the alkali compounds as they affect the mechanical and chemical properties of candidate materials.
Characterization of Engine Stabilization for Diagnostic and Acceptance Testing
Authors: Bird J. W. , Georgantas A. I. , Barry B. C. , Francoeur J. P. , House P.
Published: February 2015

Possible changes to F404 turbofan engine test procedures have been investigated to reduce cost and time. The current procedures specify either fixed waiting times or stable conditions before acquiring data for performance checks. These stabilization times can account for several thousand litres of fuel. A literature-supported, experimental study is described to quantify stabilized operation. A set of derived stabilization indices are compared to measured data. Possible reductions in single tests ranged from 30 to 200 seconds. Variations are presented resulting from ambient conditions, and the extent of throttle movement Fuel savings of 300 to 700 litres are estimated depending on the maintenance test and are projected to about $100K on an annual, fleet-wide basis. Heat transfer modelling and validation issues are also discussed.
Evaluation of Thermochemical Recuperation and Partial Oxidation Concepts for Natural Gas-Fired Advanced Turbine Systems
Authors: Rabovitser Joseph K. , Khinkis Mark J. , Bannister Ronald L. , Miao Frank Q.
Published: February 2015

An investigation into the potential benefits of thermochemical recuperation and partial oxidation in advanced natural gas-fired turbine systems is being carried out by a team consisting of the Westinghouse Electric Corporation and the Institute of Gas Technology under contract to the U.S. Department of Energy and the Gas Research Institute. The purpose of this study is to determine whether the application of thermochemical recuperation and/or partial oxidation technologies to advanced natural gas-fired power generation systems provides performance and/or cost benefits. This paper presents an overview of the concepts and technologies which are under investigation, as well as several of the thermodynamic cycles which are being developed to determine their viability.
Cost Effective Manufacturing Methods for Structural Ceramic Matrix Composite (CMC) Components
Authors: Wurtinger H. , Mühlratzer A.
Published: February 2015

MAN Technologie AG has been engaged in the field of ceramic matrix composites (C/SiC, SiC/SiC) for approximately 10 years. Two manufacturing methods have been developed with respect to economical series production:

- Chemical Vapour Infiltration Process (CVI) with temperature and pressure gradients

- Liquid Polymer Impregnation (LPI) and Pyrolysis

The advantage of these methods is an essential reduction of process time compared to the conventional isothermal-isobaric CVI method, with equivalent material performance. The main material characterization data, such as strength/strain, thermal shock, dynamic fatigue and high temperature behaviour are described. Several components under development or in low volume preseries production are presented.
Inlet Conditioning Enhances Performance of Modern Combined Cycle Plants for Cost-Effective Power Generation
Authors: Van Der Linden Septimus , Searles David E.
Published: February 2015

This paper will examine the performance enhancement and cost benefits of inlet air conditioning applied to a modern combined cycle plant at high ambients, resulting in lower electricity production costs. Site specific cases are presented to demonstrate a broad range of application and cost benefits.

The successful project in today’s aggressive competitive power marketplace is most typically defined as “lowest $/kW”. Traditional combined cycle plants have been driven to higher levels of efficiency by increasing gas turbine heat recovery using large, multiple pressure level heat recovery steam generators and improving heat sink technologies with aggressive cooling towers or air cooled condensers. This methodology rapidly produced less competitive results as the price of new generation was reduced.

The driving technology behind this change was the development of high output, high efficiency advanced gas turbines. Improved metallurgy, cooling schemes and blade coating systems permitted each GT manufacturer to offer improved output and efficiencies. These improvements, coupled with industry uncertainty due to the threat of deregulation and consequential reduction in new generation opportunities, has allowed new performance standards to be realized for equal or lower unit prices, leading to an unparalleled reduction of installed cost for new power plants.
Analysis of the Oil Film on the Inside Surface of an Aero-Engine Bearing Chamber Housing
Authors: Chew John W.
Published: February 2015

Knowledge of flow and heat transfer in bearing chambers is important in the design of engine oil systems. In this paper a simplified model of the oil film on the housing of a bearing chamber is presented and the results compared with other workers’ measurements. An integral approach is used and the analysis includes the effects of surface friction, heat transfer, gravity and swirl of the oil at inlet. Two-dimensionality is assumed with variations in the axial direction being neglected. The model is expected to apply at high rotational speeds where “rimming” dominates with the oil flowing around the drum in a continuous film. A similar rimming flow regime occurs in a rotating, horizontal drum partially filled with liquid and the present model is also tested against data for this problem.

Some good qualitative and quantitative agreement with measurements has been found, but significant discrepancies and uncertainties remain. Overall the results of this first attempt to analyse the bearing chamber flow are considered very encouraging.
Investigation of the Flow and Heat Transfer in a Low Pressure Turbine Interdisc Cavity With Skewed Radial Jetflow
Authors: Mirzamoghadam Alexander V.
Published: February 2015

Heat transfer in the low pressure turbine interdisc cavity of an aero gas turbine engine with a closed rotating outer-rim and forced radially outward jetflow directed along the downstream disc-cob front face was partially investigated by experiment and theory as part of an advanced cooling design concept study. Within the interdisc cavity, several metal temperature transient and steady state measurements in the circumferential direction as well as the 2-D axisymmetric plane at rotating speeds of 1500 rpm and 7000 rpm were made. The results are based on matching the measured metal and air temperature at both speed levels as well as the transient behavior between the two speed levels to those predicted by the 2-D axisymmetric transient thermal model. A qualitative description of the 3-D nature of the flow field is given with the aid of CFD studies. The results indicate that the skewed forced jetflow produces a stronger variation to the level of heat transfer at high rotating speed. The jetflow partially penetrates outward through the cavity providing enhanced free-disc forced convection heat transfer (approximately 25%) at high rotating speed to about 70% of the downstream disc radial length only. Toward the rim subcavities, the level of heat transfer drops considerably compared to that of a free-disc and heat transfer along the hot rotating rim and colder flange surfaces are described by flat plate natural convection. The jetflow exits the cavity at the bore of the upstream disc by turning forward within the cavity, substantially reducing the level of heat transfer along the diaphragm of this disc, and providing forced convection heat transfer on the cob whose level is higher than the rest of the upstream disc represented by natural convection. At low rotating speed, a dominating mixed convection mechanism is evident throughout the interdisc cavity with significantly lesser variation in heat transfer. A critical Gr/Re2 value of 0.02 was established as the minimum where both natural and forced convection are important. The resulting behavior in local heat transfer coefficient and Nusselt number along the hot bolted rim and the discs are compared with those of previous investigators looking at heat transfer in a rotating cavity.
Inverse Heat Transfer Engineering Design for Internally Cooled Gas Turbine Airfoils
Authors: Cunha Francisco J. T. , DeAngelis David A.
Published: February 2015

In the design and development of modern gas turbine machines for efficient power generation in combined cycle applications, nozzle segments with airfoils and sidewalls need to be effectively cooled to operate in gas temperature environments in the excess of the melting point of the material of construction. Particular attention is given to the thermal evaluation as it affects component design life and performance. In this context, an optimization methodology is prescribed for inverse determination of required coolant heat transfer as a function of hot gas conditions and subjected to constraints associated with allowable metal temperature. A general boundary element method is used in the optimization process to provide a relatively fast and economically feasible design procedure. The optimized set of heat transfer results are converged when the external metal temperatures fall within acceptable limits. Once the magnitude and distribution of required coolant heat transfer coefficients are obtained, the cooling technique can be devised using available or referenced correlations for impingement jets through insert plates, banks of pin fins, turbulators, or just simply forced convection through internal passages. An illustrative example is presented with a Joukowski airfoil using a finite element method as an alternative method of solution for comparison and verification.
Estimating Gas Turbine Internal Cycle Parameters Using a Neural Network
Authors: Chbat Nicolas W. , Rajamani Ravi , Ashley Todd A.
Published: February 2015

We show that a neural network can be successfully used in place of an actual model to estimate key unmeasured parameters in a gas turbine. As an example we study the combustion reference temperature, a parameter that is currently estimated via a nonlinear model inside the controller and is used in a number of critical mode-setting functions within the controller such as calculating the fuel-split between various manifolds. We show that a feedforward neural network using simple back propagation learning can be built for estimating combustion reference temperature. The neural network matches the accuracy of the current estimate; and it is more robust to errors in its internal parameters. This is advantageous from the point of view of implementation since a number of errors creep in when running the algorithm on a digital controller, and an estimator that is not robust with respect to such errors can degrade the performance of the whole system.
Ceramics for ATS Industrial Turbines
Authors: Wenglarz Richard , Ali Sy , Layne Abbie
Published: February 2015

The U.S. Department of Energy and most U.S. manufacturers of stationary gas turbines are participating in a major national effort to develop advanced turbine systems (ATS). The ATS program will achieve ultra-high efficiencies, environmental superiority, and cost competitiveness compared with current combustion turbine systems. A major factor in the improved efficiencies of simple cycle ATS gas turbines will be higher operating temperatures than current engines. These temperatures strain the limits of metallic alloy and flow-path cooling technologies.

Ceramics materials offer a potential alternative to cooled turbine alloys for ATS turbines due to higher melting points than metallics. This paper evaluates ceramics technology and plant economic issues for ATS industrial turbine systems. A program with the objective of demonstrating first-stage ceramic vanes in a commercial industrial turbine is also described.