bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Unsteady Compressible Viscous Layers
Authors: Power G. D. , Verdon J. M. , Kousen K. A.
Published: March 2015

The development of an analysis to predict the unsteady compressible flows in blade boundary layers and wakes is presented. The equations that govern the flows in these regions are transformed using an unsteady turbulent generalization of the Levy-Lees transformation. The transformed equations are solved using a finite difference technique in which the solution proceeds by marching in time and in the streamwise direction. Both laminar and turbulent flows are studied, the latter using algebraic turbulence and transition models. Laminar solutions for a flat plate are shown to approach classical asymptotic results for both high and low frequency unsteady motions. Turbulent flat-plate results are in qualitative agreement with previous predictions and measurements. Finally, the numerical technique is also applied to the stator and rotor of a low-speed turbine stage to determine unsteady effects on surface heating. The results compare reasonably well with measured heat transfer data and indicate that nonlinear effects have minimal impact on the mean and unsteady components of the flow.
Towards Improved Throughflow Capability: The Use of 3D Viscous Flow Solvers in a Multistage Environment
Authors: Dawes W. N.
Published: March 2015

A methodology is presented for simulating turbomachinery blade rows in a multistage environment by deploying a standard 3D Navier-Stokes solver simultaneously on a number of blade rows. The principle assumptions are that the flow is steady relative to each blade row individually and that the rows can communicate via inter-row mixing planes. These mixing planes introduce circumferential averaging of flow properties but preserve quite general radial variations. Additionally, each blade can be simulated in 3D or axisymmetrically (in the spirit of throughflow analysis) and a series of axisymmetric rows can be considered together with one 3D row to provide, cheaply, a machine environment for that row.

Two applications are presented: a transonic compressor rotor and a steam turbine nozzle guide vane simulated both isolated and as part of a stage. In both cases the behaviour of the blade considered in isolation was different to when considered as part of a stage and in both cases was in much closer agreement with the experimental evidence.
Secondary Flow Measurements in a Turbine Cascade With High Inlet Turbulence
Authors: Gregory-Smith D. G. , Cleak J. G. E.
Published: March 2015

Measurements of the mean and turbulent flow field have been made in a cascade of high turning turbine rotor blades. The inlet turbulence was raised to 5% by a grid placed upstream of the cascade, and the secondary flow region was traversed within and downstream of the blades using a 5 hole probe and crossed hot-wires. Flow very close to the end wall was measured using a single wire placed at several orientations. Some frequency spectra of the turbulence were also obtained.

The results shows that the mean flow field is not affected greatly by the high inlet turbulence. The Reynolds stresses were found to be very high, particularly in the loss core. Assessment of the contributions to production of turbulence by the Reynolds stresses show that the normal stresses have significant affects as well as the shear stresses. The calculation of eddy viscosity from two independent shear stresses show it to be fairly isotropic in the loss core. Within the blade passage, the flow close to the end wall is highly skewed and exhibits generally high turbulence. The frequency spectra show no significant resonant peaks, except for one at very low frequency, attributable to an acoustic resonance.
Parametric and Numerical Study of Fully-Developed Flow and Heat Transfer in Rotating Rectangular Ducts
Authors: Iacovides H. , Launder B. E.
Published: March 2015

This work is concerned with fully-developed constant-density turbulent flow through rectangular straight ducts rotating in an orthogonal mode. Ducts of both square and 2:1 aspect ratio cross-sections have been examined. For the square duct, predictions have been performed for Reynolds numbers of 33,500 and 97,000 and for the 2:1 aspect ratio duct the computations were carried out for a Reynolds number of 33,500. Values of the inverse Rossby number (Ro = ΩD/Wb) ranged from 0.005 to 0.2. Except in the immediate vicinity of the wall, the standard high-Reynolds-number version of the k-ε model is used to account for the effects of turbulence. Across the near-wall sublayer the damping of turbulence is modelled through a low-Reynolds-number one-equation model.

Low rotational speeds cause the formation of a pair of symmetric streamwise vortices. At higher rotational speeds, flow instabilities on the pressure side lead to transition to a more complex four-vortex structure. The transition point depends on both the cross-sectional geometry and the flow Reynolds number. Moreover, over a range of Rossby number, either two- or four-vortex solutions are possible depending upon initial conditions.

The rotation leads to significant differences between the values of friction factor and Nusselt number on the suction and pressure surfaces of the duct. The degree of heat transfer augmentation on the pressure side is found to depend on the Reynolds number as well as on Rossby number. In contrast, heat-transfer attenuation on the suction side is only Rossby-number dependent.
Local Heat Transfer in Turbine Disk-Cavities: Part I — Rotor and Stator Cooling With Hub Injection of Coolant
Authors: Bunker R. S. , Metzger D. E. , Wittig S.
Published: March 2015

Results are presented from an experimental study designed to obtain detailed radial heat transfer coefficient distributions applicable to the cooling of disk-cavity regions of gas turbines. An experimental apparatus has been designed to obtain local heat transfer data on both the rotating and stationary surfaces of a parallel geometry disk-cavity system. The method employed utilizes thin thermochromic liquid crystal coatings together with video system data acquisition and computer-assisted image analysis to extract heat transfer information. The color display of the liquid crystal coatings is detected through the analysis of standard video chromanance signals. The experimental technique used is an aerodynamically steady but thermally transient one which provides consistent disk-cavity thermal boundary conditions while yet being inexpensive and highly versatile. A single circular jet is used to introduce fluid from the stator into the disk-cavity by impingement normal to the rotor surface. The present study investigates hub injection of coolant over a wide range of parameters including disk rotational Reynolds numbers of 2 to 5 · 105, rotor/stator spacing-to-disk radius ratios of .025 to .15, and jet mass flow rates between .10 and .40 times the turbulent pumped flow rate of a free disk. The results are presented as radial distributions of local Nusselt numbers. Rotor heat transfer exhibits regions of impingement and rotational domination with a transition region between, while stator heat transfer shows flow reattachment and convection regions with evidence of an inner recirculation zone. The local effects of rotation, spacing, and mass flow rate are all displayed. The significant magnitude of stator heat transfer in many cases indicates the importance of proper stator modeling to rotor and disk-cavity heat transfer results.
Full Annular Rig Development of the FT8 Gas Turbine Combustor
Authors: Fox T. G. , Schlein B. C.
Published: March 2015

The results of developmental testing in a high pressure, full annular combustion section af the FT8 industrial gas turbine are presented. Base power conditions were simulated at approximately 60% of burner pressure. All aspects of combustion performance with liquid fuel were investigated, including starting, blowout, exit temperature signature, emissions, smoke and liner wall temperature. Configurational changes were made to improve liner cooling, reduce emissions, adjust pressure loss and modify exit temperature profile. The effects of water injection on emissions and performance were evaluated in the final test run. Satisfactory performance in all areas was demonstrated with further refinements to be carried out during developmental engine testing.
Chemical Composition of Exhaust From Aircraft Turbine Engines
Authors: Spicer Chester W. , Holdren Michael W. , Smith Deborah L. , Hughes David P. , Smith Mark D.
Published: March 2015

This paper reports measurements of the chemical composition of exhaust from two aircraft turbine engines. The two engines are the F101, used on the B-1B aircraft, and the F110, used on the F-16C and F-16D aircraft. Samples were collected from each engine using a probe positioned just behind the exhaust nozzle. The measurements reported here were made at four power settings from Idle to Intermediate power. Exhaust composition measurements included carbon monoxide, carbon dioxide, nitrogen oxides, total hydrocarbons, and individual organic species. The principle focus of this paper is on the detailed organic species results.
A Computational Procedure for Diffuser-Combustor Flow Interaction Analysis
Authors: Karki K. C. , Oechsle V. L. , Mongia H. C.
Published: March 2015

This paper describes a diffuser-combustor flow interaction analysis procedure for gas turbine combustion systems. The method is based on the solution of the Navier-Stokes equations in a generalized non-orthogonal coordinate system. The turbulence effects are modeled via the standard two-equation (k-ε) model. The method has been applied to a practical gas turbine combustor-diffuser system that includes support struts and fuel nozzles. Results have been presented for a three-dimensional simulation, as well as for a simplified axisymmetric simulation. The flow exhibits significant three-dimensional behavior. The axisymmetric simulation is shown to predict the static pressure recovery and the total pressure losses reasonably well.
Limit Cycle Vibration Analysis of a Long Rotating Cylinder Partially Filled With Liquid
Authors: Colding-Jørgensen Jørgen
Published: March 2015

The dynamics of a long, stiff cylinder, flexibly suspended at the ends, partially filled with liquid, is analyzed for varying rotating speed.

It appears from the analysis that in the absence of external damping, two distinct speed ranges with unstable whirl are present, as opposed to one instability region for the short cylinder which has been analyzed by a number of authors (Kuipers, 1964), Wolf (1968).

This is in agreement with field experience with centrifuges, where several regions of instability are often encountered, each corresponding to a particular vibration mode. The results should also apply to a jet engine with oil accidentally trapped in the rotor, or any hollow rotor with liquid trapped in the cavity.

When external damping is applied, the linear theory predicts the rotor be unstable at all speeds (Kuipers, 1964).

This is clearly not in accordance with field experience, and other authors have suggested different types of non-linear analysis which can give finite amplitude stable whirl or pulsating whirl (Berman et al., 1985).

In the present analysis a simplified non-linear analysis known as the hydraulic jump approximation is applied in the two unstable speed ranges predicted by the linear theory, and a stable whirl finite amplitude, dependent on the external damping, follows.

It is argued that the amplitudes found this way should always be higher than those predicted by a more sophisticated analysis, and also higher than the amplitudes measured by other authors, so that the procedure described should give a safe worst case prediction of rotor whirl amplitudes for a given external damping.

Finally, an experimental setup which is intended to verify the analysis in a quantative way is presented.
Effect of Incidence on Wall Heating Rates and Aerodynamics on a Film Cooled Transonic Turbine Blade
Authors: Camci Cengiz , Arts Tony
Published: March 2015

This study investigates the influence of incidence on convective heat transfer to highly curved surfaces of a film cooled turbine rotor blade. A computational study of free stream inviscid aerodynamics without cooling at various incidences is followed by well documented measured heat transfer data sets. The heat transfer experiments are discussed for cases with and without film cooling, performed under realistic gas turbine flow conditions in the short duration heat transfer facility of the von Karman Institute for Fluid Dynamics. The precise location of the stagnation point and the iso-Mach number contours in the passage for each incidence (−10°, 0°, 10°, +10°) are presented for a nominal exit Mach number of 0.94. The free stream mass flow rate was kept constant for each experiment at different incidence levels. Three rows of compound angled discrete cooling holes are located near the leading edge in a shower-head configuration. Two rows of staggered discrete cooling holes are located on the suction side and a single row of cooling holes is located on the pressure side. The short duration measurements of quantitative wall heat fluxes on nearly isothermal blade surfaces both in the presence and absence of coolant ejection are presented. The study indicated that the change of the position of the stagnation point strongly altered the aerodynamic behaviour and convective heat transfer to the blade in approximately the first 30 % of both the pressure side and the suction side in the presence and absence of film cooling. The immediate vicinity of the stagnation point was not significantly affected by changing incidence without cooling. Transitional behaviour both on the suction surface and on the pressure surface was significantly influenced by the changes in approching flow direction. Flow separation associated with incidence variations was also observed. Extremely low levels of convective heat transfer coefficients were experienced near the regions where small separation bubbles are located.
Experimental Study of the Swirling Flow in the Volute of a Centrifugal Pump
Authors: Elholm T. , Ayder E. , Van Den Braembussche R.
Published: March 2015

The detailed three-dimensional velocity distributions, corresponding to design and off-design operation, were measured in two different circumferential cross sections of a volute by means of LDV. It is shown that the swirl has a forced vortex type velocity distribution and that the location of the swirl center is changing with mass flow. The through flow velocity distribution is primarily defined by the conservation of angular momentum. A strong interaction between the through flow and swirl velocity is observed.

Flow visualisation in the tongue region reveals a reversal of the velocity at the volute inlet with increasing mass flow. The pressure drop between volute outlet and inlet at low mass flow pushes extra fluid through the tongue gap and increases the mass flow in the volute. The abrupt pressure rise at high mass flow results in local return flow perturbing the flow in the outlet pipe.
Turbulent Combustion Properties Behind a Confined Conical Stabilizer
Authors: Pan J. C. , Schmoll W. J. , Ballal D. R.
Published: March 2015

Turbulence properties were investigated in and around the recirculation zone produced by a 45° conical flame stabilizer of 25% blockage ratio confined in a pipe supplied with a turbulent premixed methane-air mixture at a Reynolds number of 5.7 × 104. A three-component LDA system was used for measuring mean velocities, turbulence intensities, Reynolds stresses, skewness, kurtosis, and turbulent kinetic energy.

It was found that wall confinement elongates the recirculation zone by accelerating the flow and narrows it by preventing mean streamline curvature. For confined flames, turbulence production is mainly due to shear stress-mean strain interaction. In the region of maximum recirculation zone width and around the stagnation point, the outer stretched flame resembles a normal mixing layer and gradient-diffusion closure for velocity holds. However, and in the absence of turbulent heat flux data, counter-gradient diffusion cannot be ruled out. Finally, and because of the suppression of mean streamline curvature by confinement, in combusting flow, the production of turbulence is only up to 33% of its damping due to dilatation and dissipation.
Acoustic Design of Lightweight Gas Turbine Enclosures
Authors: Rawlinson R. D.
Published: March 2015

Acoustic enclosures for the gas turbine industry have to comply with a number of stringent safety requirements including structural strength, fire resistance and sound insulation. This has led traditionally to heavy enclosure designs.

Corrugated enclosure panels offer significant structural advantages because of their increased bending stiffness. Consequently, a corrugated panel of a given thickness can give the same structural strength as a flat panel of substantially greater weight and thickness. But corrugated panels are intrinsically less effective as a sound insulator than flat panels of the same thickness.

This paper examines the implications of corrugated, lightweight panels for acoustic enclosures. It illustrated that, by careful design, the inherent acoustical disadvantages of corrugated panels can be overcome so that thinner, lighter and more cost-effective enclosures can be used without compromising the overall structural and acoustical design requirements.
Announcing the LM1600 Marine Gas Turbine Module
Authors: Beiner Christian , Latterman Ruprecht
Published: March 2015

Motoren- und Turbinen- Union Friedrichshafen (MTU) and General Electric Marine and Industrial Engines (GE) are cooperating in the development of an LM1600 marine gas turbine propulsion module similar to the GE LM2500 marine module.

The GE LM1600 marine gas turbine is described and an outline of the engine performance characteristics is given.

MTU’s design goals and the respective design approaches of essential sub-systems are presented: General arrangement of the module with the installed gas turbine and exhaust collector, base frame with engine and exhaust collector mounting links, shock mounts, acoustic enclosure and the corresponding internal and external auxiliary systems, e.g., lube-oil storage and conditioning assembly, fuel system, engine cooling system, high-speed coupling shaft and ice condition detection system. The interface requirements for combustion air, cooling air and exhaust stacks as well as the interface for vessel piping and wiring are described.

Finally, some LM1600 ship machinery arrangements for CODOG, CODAG and possibly COGAG propulsion systems in future applications are presented.
Numerical Investigation of the Three-Dimensional Temperature Field in the Near Hole Region of a Film Cooled Turbine Vane
Authors: Coudray X.
Published: March 2015

The increased severity of the thermal environment of high pressure turbine blades and vanes requires accurate calculations for the successful design of these parts. In this paper, the prediction of the temperature field in the near-cooling-hole region on a film cooled turbine vane is presented. The surface distribution of the heat transfer coefficient and the film cooling effectiveness on the vane in presence of one or several film cooling injections is obtained from boundary layer calculations and via experimental correlations. Cooling jet coalescence is taken into account as well as the main parameters governing this physical phenomenon. The internal boundary conditions result from available correlations. The study was conducted on two different configurations : a flat plate including an injection through two rows of holes and a turbine vane including three injections through two rows of holes on the suction side. Thermal computations using a three-dimensional finite element code yield strong temperature distortions and high temperature gradients around the injection zones. The study also indicates that the three-dimensional temperature field just downstream of the injections becomes two-dimensional when jet coalescence takes place. The influence of one or several obstructed injection holes on the temperature field is studied; important effects are observed when the main flow temperature is high.
Performance Prediction of Subsonic Separated Cascades
Authors: Yazigi N. , Charlier M. H. , Gerolymos G. A. , Chauvin J.
Published: March 2015

During the design process of fans and compressors, rapid computation of performance characteristics at various operating points is essential. In view of estimating off-design performance, the prediction of compressible separated flow is needed.

A method has been developed for predicting such flows in 2-D cascades, with varying blade-height, based on an iterative viscous-inviscid interaction approach. Inviscid flow is simulated using a panel method. The effects of compressibility and streamsheet convergence or divergence are taken into account by singularities distributed in the interior of the flowfield.

Viscous flow is simulated using an integral boundary-layer method, till the point of separation. Laminar and transitory separation bubbles are modelled semi-empirically. Separated-flow regions are simulated using a free streamline model.

The method has been systematically compared with available experimental data and has shown very good agreement concerning the prediction of pressure distribution, deviation angle and loss coefficient, from negative to positive stall and for a wide range of Reynolds number and subsonic Mach number. The method is an interesting performance analysis tool due to its rapidity and reliability.
Further Development of an Improved Pulse, Pressure Gain, Gas-Turbine Combustor
Authors: Kentfield J. A. C. , Fernandes L. C. V.
Published: March 2015

Further development work is described, which included both theoretical analysis and experimental testing, of an improved prototype, valveless, pulse, pressure gain, combustor for gas turbines. The analytical work involved the application to the non-steady flow in the combustor secondary flow duct of the method-of-characteristics as used for one-space dimensional, time dependent, compressible flows. Gas temperatures in the secondary flow duct were measured experimentally as were the pressure gain, due to the pulse combustor, and the overall efficiencies of the gas generator type gas-turbine with both the conventional steady flow combustor and the alternative pulse, pressure gain, combustor. It was concluded that the analytical work confirmed earlier experimental findings showing the benefits of restricting the secondary flow duct exit area. It was also concluded that the use of the pulse combustor resulted in a maximum improvement of 27% in the thermal efficiency of the small, low pressure-ratio, educational, gas generator turbo-machine.
A Study of Isothermal Flow Past a Confined Bluff Body
Authors: Lai M. K. Y. , D’Souza M. V. , Campbell I. G. , Smallwood G. J. , Snelling D. R.
Published: March 2015

The paper describes a preliminary assessment of a TEACH-based mathematical model, known as TURCOM, for isothermal flow past a confined bluff-body. The assessment is based on comparisons of numerical predictions with the experimental data. Laser Doppler Velocimetry (LDV) and gas analysis were used to measure radial profiles of axial velocity and CO2 concentration. Laser sheet illumination was employed to study the gross features of the flow.

Depending on the jet velocity ratio, two or three recirculation zones and two well-defined stagnation points along the centerline were predicted. Agreement between the predictions and experimental data were reasonably good, but the axial location of the fuel stagnation point was under-estimated when compared with the LDV data. Flow visualization indicated vortex shedding off the edges of the bluff body, an unsteady flow phenomenon that neither TURCOM prediction nor LDV measurements could identify.
Flow Behavior in a Dump Diffuser With Distorted Flow at the Inlet
Authors: Honami Shinji , Morioka Tadashi
Published: March 2015

The cold flow experiments are made in a two-dimensional dump diffuser. Behavior of an impinging jet over a flame dome head and its reattachment to the casing wall is presented, when a symmetric or distorted flow is provided at the diffuser inlet. A hot-wire anemometer and laser doppler velocimeter are used. Diffuser performances of the pressure recovery and total pressure loss on three types of pre-diffuser geometry and four cases of dump gap between pre-diffuser exit and flame dome head are tested.

Both pre-diffuser geometry and dump gap are dominant parameters affecting pressure recovery and total pressure loss. A small dump gap causes insufficient pressure recovery in the pre-diffuser, resulting in a loss of total pressure in the diffuser. Distribution of the flow rate to the branched channels is relatively insensitive to the inlet velocity profile with distortion, as the shift of the jet stream occurs just upstream of the flame dome head.
Model Adjustment of Small Rotors for High Speed Gas Turbines
Authors: Delbez Alain , Beth Christian , Gay Daniel
Published: March 2015

In this paper, we present the studies which are carried out at MICROTURBO relating to rotor-bearing systems mounted in small high speed gas turbines.

These studies are based on both theoretical and experimental approaches, and are aimed at providing an improved prediction of the dynamic behaviour of rotors at the design stage, in particular the critical angular velocities and sensitivity to unbalance.
Prediction and Measurement of Film Cooling Effectiveness for a First-Stage Turbine Vane Shroud
Authors: Granser D. , Schulenberg T.
Published: March 2015

After compressor discharge air has initially been used to cool the heat shields of the hot gas inlet casing, it can subsequently be employed for film cooling of the first-stage vane shrouds. Since the flow field near these shrouds is three-dimensional, the film cooling effectiveness cannot be predicted correctly by common two-dimensional codes. The secondary flow transports the film from the pressure side to the suction side where it can even climb up the airfoil to cool its trailing section.

Such film cooling effectiveness was first investigated experimentally in a linear vane cascade at atmospheric pressure. The temperatures and static pressure levels at the adiabatic shrouds, as well as the temperature measurements within the vane cascade, are reported for different cooling film blowing rates.

In addition, the secondary flow was analysed numerically using a partially-parabolic computer code for 3D viscous flows. It involves mutual interaction of the boundary layer with the mainstream. The secondary flow can also be modelled with this algorithm, which requires less numerical effort than solving the fully 3D elliptic flow equations. The numerical results of the experiment and numerical predictions are compared. In addition, the application of these results to a high-temperature gas turbine is presented.
A Study on the Blade Shape Influence on Flow Distribution and Performance in Centrifugal Compressor Rotors
Authors: Tuccillo Raffaele , Senatore Adolfo
Published: March 2015

The authors present an analysis of the flow through a centrifugal compressor rotor. A quasi-3D flow model evaluates the interaction of the meridional and blade-to-blade solution, so as to determine the flow pattern inside an inviscid region.

A further interaction is then considered between the non-viscous flow and the boundary layers which grow along the end-walls and the blade surfaces. This makes it possible both to determine a more realistic flow condition, because of the blockage effects exerted by the boundary layers, and to estimate the total pressure losses related to the momentum thickness.

Examples are presented for a compressor of an aircraft engine. The influence of blade shape on the above described phenomena is analyzed, starting from the actual rotor geometry and making a parametric study of the alterations in flow pattern produced by changes in meridional blade shape, inlet and outlet flow areas, and splitter blades.

The analysis will provide a basis for future activities involving the use of optimizing techniques for the final choice of the blade characteristics.
Introduction to the Basic Technology of Stealth Aircraft: Part 1 — Basic Considerations and Aircraft Self-Emitted Signals — Passive Considerations
Authors: Howe D.
Published: March 2015

This paper reveiws the information which may be used by a potential enemy to detect and track an aircraft. In particular it is concerned with a passive approach by the enemy, namely the interception of acoustic, infra-red, visual and miscellaneous self-emissions. The origins of these emissions are described and means of eliminating them or reducing their intensity are discussed. Emphasis is placed on the impact of these so called stealth techniques on the design of the aircraft as a whole.
Introduction to the Basic Technology of Stealth Aircraft: Part 2 — Illumination by the Enemy — Active Considerations
Authors: Howe D.
Published: March 2015

One of the most significant considerations of stealth technology is the technique used to reduce the probability of detection of an aircraft by radar. This paper is concerned with the nature of the various contributions to the radar cross section, and the means by which their effect may be reduced. A survey of the impact of stealth technology on some specific designs is included, from which the conclusion is drawn that the achievement of good stealth characteristics demands attention to both the overall configuration and detail design.
Investigation of the Flow at the Exit of an Unshrouded Centrifugal Impeller and Comparison With the “Classical” Jet-Wake Theory
Authors: Rohne K.-H. , Banzhaf M.
Published: March 2015

L2F measurements of the flow at the exit of modern unshrouded centrifugal impellers with backswept blades yield a much more uniform velocity profile compared to former measurements on impellers with radial blading. Further evaluations show that the “classical” jet-wake theory assuming an isentropic jet and a wake flow congruent with the shape of the blade at the impeller exit needs correction in order to obtain meaningful results when interpreting thermodynamic measurements on centrifugal compressor stages.
Impeller Flow Field Measurement and Analysis
Authors: Fagan John Robert , Fleeter Sanford
Published: March 2015

A series of experiments are performed to investigate and quantify the three-dimensional mean flow field in centrifugal compressor flow passages and to evaluate contemporary internal flow models. The experiments include the acquisition and analysis of LDV data in the impeller passages of a low speed moderate scale research mixed-flow centrifugal compressor operating at its design point. Predictions from a viscous internal flow model are then correlated with these data. The LDV data show the traditional jet-wake structure observed in many centrifugal compressors, with the wake observed along the shroud 70% of the length from the pressure to suction surface. The viscous model predicts the major flow phenomena. However, the correlations of the viscous predictions with the LDV data were poor.
Turbine Preliminary Design Using Artificial Intelligence and Numerical Optimization Techniques
Authors: Tong Siu Shing , Gregory Brent A.
Published: March 2015

This paper describes a new software approach to the preliminary design of aircraft engine turbines. A hybrid artificial intelligence and numerical-optimization-based design shell called Engineous was used to capture some basic turbine preliminary design knowledge, manipulate turbine design parameters, execute a turbine performance prediction program and its preprocessors, and analyze results. Engineous automatically supplements incomplete human design knowledge with symbolic and numerical search techniques when needed. This approach produced designs with higher predicted performance gains than the existing manual design process in a tenth of the turnaround time and has yielded new insights into turbine design. A comparison of turbine designs obtained by designers and by Engineous is presented here along with an overview of Engineous system architecture.
Experimental and Numerical Investigation of Three-Dimensional Viscous Flows and Vortex Motion Inside an Annular Compressor Blade Row
Authors: Gallus H. E. , Hah C. , Schulz H. D.
Published: March 2015

A detailed experimental and numerical investigation was carried out to examine the three-dimensional flow field, secondary flows and vortex motion in an annular compressor cascade.

Various flow visualizations near the blade surface and endwalls, wall static pressure and loss measurements, as well as hot-film and hot-wire measurements inside the blade boundary layers were performed at various flow rates to understand the complex flow phenomena. A Reynolds-averaged Navier-Stokes equation was solved to investigate the flow numerically.

The detailed comparison between measurement and numerical prediction indicates that the complex three-dimensional flow phenomena (corner stall, vortex motion, radial mixing, etc.) is very well predicted with the numerical method.
Second Generation Low-Emission Combustors for ABB Gas Turbines: Burner Development and Tests at Atmospheric Pressure
Authors: Sattelmayer Th. , Felchlin M. P. , Haumann J. , Hellat J. , Styner D.
Published: March 2015

Based on fundamental research concerning swirling flows, including the vortex breakdown phenomenon, as well as on stability considerations of premixed flames, a second generation of low emission burners has been developed.

The lean premixing technique provides NOx-emissions below 25ppmv for natural gas. For liquid fuels the oxides of nitrogen are limited to 42ppmv (oil no. 2).

The novel burner technology will be applied to the well-known ABB silo combustor. As a first step the Conical Premix Burner will be used to retrofit the ABB type 11N. For the ABB gas turbine type 8 the design of a novel fully annular combustor is in progress.

Most of the conceptual work concerning burner aerodynamics and burner-burner interaction has been carried out on scaled-down burner- and combustor-models. For a second step a sector of the combustor in 1:1 scale has been tested at atmospheric pressure. Additional high pressure tests provide information about the combustor performance at engine conditions.

The present paper summarizes the results of the first two steps beginning with the early ideas in the conceptual phase up to the 1:1 tests which prove the low-NOx capability for both gaseous and liquid fuels under atmospheric pressure conditions.
Repowering of Thermal Power Plants by Means of a Closed Cycle MHD Topper
Authors: Bellofatto Oreste , Borghi Carlo A.
Published: March 2015

A repowering approach of existing thermal power plants through closed cycle MHD toppers is presented in this note. In order to maintain the generating capacity of the steam unit at its nominal value, a modification of the boiler allowing an increase of the combustion product mass flow of 1.6–1.8, is calculated. The high value of the electrical power density, when compared with the thermal losses, obtained by the MHD channel indicates that this system is suitable for small/medium scale plants. An electrical power generated by the retrofitted plant of about 2 time the value of the existing unit and a gain in overall efficiency of 5–8 percentage points are obtained.
Rolling Wear of Silicon Nitride Bearing Materials
Authors: Lucek John W.
Published: March 2015

Rolling-contact fatigue test methods were used to measure the wear performance of several silicon nitride materials. Sintered, hot pressed and hot isostatically pressed materials exhibited wear rates ranging over three orders of magnitude. Hot isostatically pressed materials had the lowest wear rates. Despite the disparity in wear performance, all materials tested had useful rolling-contact fatigue lives compared to steel. Fatigue life estimates, failure modes, and rolling wear performance for theses ceramics are compared to M-50 steel.

This work highlights the rapid contact stress reductions that occur due to conformal wear in rolling-contact fatigue testing. Candidate bearing materials with unacceptably high wear rates may exhibit useful fatigue lives. Rolling contact bearing materials must possess useful wear and fatigue resistance. Proper performance screening of candidate bearing materials must describe the failure mode, wear rate, and the fatigue life. Guidelines for fatigue testing methods are proposed.
Performance of Silicon Nitride (Si3N4) Components in Aerospace Bearing Applications
Authors: Ebert F. J.
Published: March 2015

Reliability is the most important criteria in aerospace applications. This paper outlines the results of investigations and functional tests performed with hybrid bearings, ceramic bearings in comparison to all-steel bearings, to demonstrate the fatigue behaviour and reliability of silicon nitride components used in rolling bearings. The performance under specific operating conditions such as high speed, blade-loss and oil-off operation is outlined in this paper as well as comparative results of friction torque and bearing temperature.
Unsteady Heat Transfer Measurements on a Rotating Gas Turbine Blade
Authors: Hilditch M. A. , Ainsworth R. W.
Published: March 2015

Heat transfer measurements made on the rotor blade of a full stage model turbine operating at engine representative conditions are presented. The measurement technique of mounting thin film heat transfer gauges on enamel coated turbine blades enables the heat transfer rate to be measured across a frequency range of d.c. to 100kHz. The output is amplified using electronic circuits housed inside the shaft before transmission through a slipring and digital signal processing routines are used to calculate the heat transfer rate. A calibration experiment in which the gauge is pulsed with a laser beam is described in detail.

The results are compared with data from a previous two-dimensional simulation of wake-passing flow on the midheight section of the same blade. The mean heat transfer rate recorded in the two experiments shows reasonable agreement. Fluctuations in the unsteady heat transfer signal at NGV passing frequency are seen at the same locations in data from both experiments, however the magnitude of the fluctuations seen on the rotor are much smaller than those recorded in the two-dimensional simulation. Frequency spectra and correlation analysis of heat transfer traces recorded on the rotor are also presented.
A New Air Filtration System Concept for Space Limited Applications and Retrofits
Authors: Cuvelier L. , Belcher M. D.
Published: March 2015

The need for adequate inlet air treatment for combustion gasturbines has been recognized for years. The benefit of high efficiency air filtration, mainly in high ambient dust environments does not require any further discussion as the shortfalls of the multi-stage static systems are known. The size of the conventional automatic pulse jet self cleaning airfilters is a serious handicap when considering upgrading/retrofitting outdated static filter systems or for any application in very limited spaces.

The new filter concept is described. It is an automatic Pulse Jet high efficiency self cleaning filter in which the major limiting factor of the previous design has been turned into an upgrading feature; the incoming air velocity direction basically eliminates the well-known pulsed dust re-entrainment. Other key design characteristics allow for capitalizing upon the reduced foot print area and justify the technical and economical replacement of the out-of-date filters with no or minor changes to the support structure. The system can in certain cases be incorporated within the old filterhouse itself.

Additional interesting features are discussed, supported by laboratory test results and field data from units operating in various environmental conditions.
Large ‘Single Blade’ Diverters and Beyond
Authors: Heller R. N. , Hearnden T. H. , Squirrell A. F. , Allshouse R. G.
Published: March 2015

‘Single-Blade’ Diverters are now a standard component of gas turbine combined cycle and co-generation plants. The paper explains the key features which have to be considered in selecting a Diverter, such as the sealing system, flap assembly construction, drive components and actuation systems. Further the latest hydraulic operating systems are described. With these it is now possible to use Diverters to finely regulate the heat input to the recovery system as well as to switch over rapidly to simple cycle operation or auxiliary firing. Finally the paper shows how it is possible with a two module Diverter to avoid using separate Isolators (dampers) even for the largest gas turbines currently available.
Direct Heat Cogeneration Applications for Kaolin Producers
Authors: Hill Jane P.
Published: March 2015

Direct heat cogeneration using gas turbines presents an unusually attractive means of supplying two end products when both are required simultaneously. Most cogeneration applications involve steam as the thermal end product. While steam has many industrial and commercial uses, the conversion of thermal output to usable steam involves losses in the heat recovery steam generator (HRSG). When the heat rejected by a gas turbine can be used directly, system losses can be minimized. One such application exists in the kaolin industry.

Kaolin is a white alumina-silicate clay used in many products, including paper, medicines, plastics and paints. One step in producing kaolin requires large spray dryers, the heat for which can be supplemented by cogeneration.

This study outlines conditions necessary to achieve economic viability with cogeneration and suggests ways to maximize economic benefits. Risks associated with cogeneration ventures are also discussed.
Energy Conservation With Catalytic Cracking in the Refinery
Authors: Najjar Yousef S. H.
Published: March 2015

Fluidized-bed catalytic cracking is one of the most commonly used processes in petroleum refining to convert heavy high-boiling point components of crude oil into gasoline and distillate components.

An energy conservation measure for such a process, utilizes an axial flow compressor which furnishes air for combustion in the regenerator where the coke deposits are burned off the catalyst and also drives the catalyst through the system.

The flue gases from the regenerator are expanded in an expansion turbine which drives the compressor, whereas the excess energy is used to drive an electric generator. The exhaust gases are utilized further in a heat recovery boiler to produce process steam.

A parametric study involving variation of air pressure and expander inlet temperature using specially devised computer program, was used to analyse the performance of the proposed system. Furthermore, the system is economically evaluated and compared with the conventional cracking system using a gas turbine engine. The proposed system offers leading performance and economic advantages in comparison with the conventional one.
A Comparison of Forming Technologies for Ceramic Gas-Turbine Engine Components
Authors: Hengst R. R. , Heichel D. N. , Holowczak J. E. , Taglialavore A. P. , McEntire B. J.
Published: March 2015

For over ten years, injection molding and slip casting have been actively developed as forming techniques for ceramic gas turbine components. Co-development of these two processes has continued within the U.S. DOE-sponsored Advanced Turbine Technology Application Project (ATTAP). Progress within ATTAP with respect to these two techniques is summarized. A critique and comparison of the two processes are given. Critical aspects of both processes with respect to size, dimensional control, material properties, quality, cost, and potential for manufacturing scale-up are discussed.
Fabrication of ATTAP Ceramic Turbine Components
Authors: Ohnsorg R. W. , Funk J. E. , Lawler H. A.
Published: March 2015

The development and fabrication of sintered alpha SiC injection molded axial rotors and slip cast vortexes by Carborundum for the Advanced Turbine Technology Applications Project (ATTAP) are discussed. Key injection molding process variables and their levels were identified through modeling and experimental design. Post-HIPing improved the density, strength, and uniformity of injection molded components. The fabrication and strength of slip cast components were enhanced through dispersion and powder beneficiation studies. The component process optimization approaches and current status are presented for each.
Transient Performance and Behaviour of Gas Turbine Engines
Authors: Torella G.
Published: March 2015

The paper deals with some activities carried out for setting up and using numerical computer codes for simulating the behaviour of gas turbine engines during transient operations.
VATEMP: The Variable Area Turbine Engine Matching Program
Authors: Roy-Aikins J. E. A. , Palmer J. R.
Published: March 2015

Variable geometry in key gas turbine components offers the advantage of either improving the internal performance of a component or of re-matching the engine cycle to alter the flow-temperature-pressure relationships. Future gas turbines are expected to use variable geometry components extensively if they are to overcome some of the problems encountered by present day engines at off-design conditions in order to give much more advanced performance. Greater attention is also being paid to the impact of installation losses on the performance of aircraft engines.

A computer program called VATEMP, herein described, has been developed capable of simulating the steady-state performance of arbitrary gas turbines with or without variable geometry in almost any gas path component. Results obtained from the program led to the conclusion that variable geometry components have the potential to improve significantly the off-design performance of gas turbines.
Gas Turbine With Intermediate Heat Exchanger for Flight Application
Authors: Shapiro J. , Levy A.
Published: March 2015

High power/weight ratio and low SFC are the most important requirements for an airborne engine. This may be achieved by a gas turbine engine with an intermediate heat exchanger, combined with a double-decked compressor-turbine design. In this engine, the specific fuel consumption is minimal at 70% of maximum power output for best fuel economy in helicopter engines. The additional weight, due to its design, is compensated by fuel saved in less than one hour flight for a 926 kW cruise power engine.
Laser Surface Melting of Thermally Sprayed Coatings and Effects on the Erosion Behaviors of Coatings
Authors: Sun Jia Shu
Published: March 2015

In this work the effects of laser melting on the microstructure and the solid particle erosion behavior of flame sprayed Ni-Cr-B- and Fe-Cr-B-alloy coatings, plasma sprayed chromium carbide (Ni-Cr) and (WC-Co) (Ni-Cr) alloy coatings have been studied. The results have shown that laser melting has modified the microstructure of sprayed coatings, eliminated the porosity of sprayed coatings and increased the erosion resistance of the coatings. The erosion mechanisms of these coatings have been investigated.
Innovations in Refurbishing Gas Turbine Components
Authors: Walker Colin , Cosart Joseph
Published: March 2015

This paper deals with the continuing development of repair methods for turbine hot gas path components.