bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Flow and Turbulence Measurements Downstream of a Backward Centrifugal Impeller
Authors: Ubaldi Marina , Zunino Pietro , Cattanei Andrea
Published: March 2015

The paper presents the results of an experimental investigation on the three-dimensional relative flow at the exit of the backward bladed centrifugal impeller of the high pressure stage of a two stage biregulating pump-turbine model, operating at the pump nominal point.

Mean velocity, Reynolds stress tensor and total pressure of the relative flow have been measured with stationary hot wire probes and fast response miniature pressure transducers, by means of a phase locked ensemble average technique.

The results, shown in terms of secondary vector plots and contours of mean flow characteristics and Reynolds stress components, give a detailed picture of the flow kinematic structure and of the complex relative total pressure loss and turbulence distributions.

In spite of strongly backswept blades, the flow leaving the impeller presents a jet and wake structure and an intense secondary flow activity. Large relative total pressure losses affect the wake and the region where secondary vortices interact.

The turbulence data analysis provides information about the effects of the impeller rotation on the turbulence structure and about the mechanisms of the flow mixing process and of the secondary flow decay downstream of the impeller.
On the Conservation of Rothalpy in Turbomachines
Authors: Lyman F. A.
Published: March 2015

The conditions under which rothalpy is conserved are investigated by means of the energy and moment-of-momentum equations for unsteady flow of a viscous, compressible fluid. Differential and integral equations are given for the total enthalpy and rothalpy in both stationary and rotating coordinates. From the equations in rotating coordinates it is shown that rothalpy may change due to: (1) pressure fluctuations caused by flow unsteadiness in the rotating frame; (2) angular acceleration of the rotor; (3) work done by viscous stresses on the relative flow in the rotating frame; (4) work done by body forces on the relative flow; (5) changes in entropy due to viscous dissipation and heat transfer. Conclusions of this investigation are compared with those of previous authors, some of whom have stated that rothalpy is conserved even in viscous flows. A modified Euler’s turbomachine equation which includes viscous effects is derived and errors in previous derivations noted.
Deposition of Volcanic Materials in the Hot Sections of Two Gas Turbine Engines
Authors: Kim J. , Dunn M. G. , Baran A. J. , Wade D. P. , Tremba E. L.
Published: March 2015

This paper reports the results of a series of tests designed to determine the melting and subsequent deposition behavior of volcanic ash cloud materials in modern gas turbine engine combustors and high pressure turbine vanes. The specific materials tested were Mt. St. Helens ash and a soil blend containing volcanic ash (black scoria) from Twin Mountain, New Mexico. Hot section test systems were built using actual engine combustors, fuel nozzles, ignitors, and high pressure turbine vanes from an Allison T56 engine can-type combustor and a more modern Pratt and Whitney F-100 engine annular-type combustor. A rather large turbine inlet temperature range can be achieved using these two combustors. The deposition behavior of volcanic materials as well as some of the parameters that govern whether or not these volcanic ash materials melt and subsequently deposit are discussed.
Performance and Emission Levels in Gas Turbine Plants
Authors: Bozza Fabio , Tuccillo Raffaele , Fontana Gustavo
Published: March 2015

The rise in gas turbine combustion chamber temperatures requires optimal choices to be made with regard not only to performance parameters but also with a view to resolving pollutant emission problems. For this reason, the authors have set up a gas turbine cycle model which performs an accurate analysis of several processes, in terms of operating fluid chemical and thermodynamic properties. The model also enables prediction of NOx formation based upon chemical kinetics and is able to relate the amount of pollutants to a number of operating parameters (e.g. cycle pressure ratio, fuel to air equivalence ratio, residence time in combustion chamber, etc.). It can also predict the effect of the most usual NOx reduction systems, such as water or steam injection.

A comparison of several possible choices for the gas and combined cycles is then presented, in terms of thermodynamic performance (e.g. first and second law analysis) and nitric and carbon dioxide emissions. In order to find the best compromise between performance improvement and limitation of pollutant emission, enhanced gas cycles are also considered, such as STIG or intecooled-reheat cycles.

Examples also refer to medium or low BTU gases, obtained from coal gasification, in order to show not only the possible advantages in terms of thermal NOx reduction, but also the significant amounts of “fuel NOx“ which can arise from ammonia contained in the fuel.
The Optimum Value of the Nozzle Outlet Angle of Turbine Stages
Authors: Kosowski Krzysztof
Published: March 2015

The paper presents the results of theoretical research on the influence of the main design parameters on the optimum value of the nozzle outlet angle. The analysis was carried out for the stages with the disc and the drum rotors. The cascade losses were determined using Traupel’s and Bammert’s generalized cascade data. The calculations have proved that the blade height, the profile chord and the number of stages in the group are the most important factors influencing the optimum nozzle outlet angle.
Analysis of Normal Mode Localization in Mistimed Bladed-Disc Assembly With Disc Coupling
Authors: Zhang Yong-Qiang , Wang Wen-Liang
Published: March 2015

This paper deals with the realistic bladed-disc assembly model, which can account for the flexibility of the disc, and investigates the occurence of localization of the vibratory modes in such assemblies. To this end, the generalized Benfield-Hruda transformation method is employed to obtain the mathematical model of the mistuned system, where both disc and blades are considered as flexible vibrating bodies. Moreover, small parameter method for clustered eigenvalves based essentially on the Ritz analysis is made use of to overcome the computational difficulties caused by mistuning and the large number of the d.o.f. of the realistic system. It is demonstrated that normal mode localiztion in realistic mistuned bladed-disc assemblies is most likely to occur when the blades are flexible enough compared with the disc, and the localized modes are mainly the low frequency ones. Finally, criteria capable of predicting the occurence of localization are discussed in this paper.
Design Features Influencing the Distribution of Fuel Within the Spray From an Air Blast Fuel Injector
Authors: Stringer F. W. , Irwin A. N.
Published: March 2015

This paper describes work carried out to determine the influence of several design features upon the performance of an air blast fuel injector. The design features studied were the number of tangential fuel holes feeding the swirl chamber, the depth of the swirl chamber, and the shape of the downstream section of the swirl chamber.

The performance parameters considered were, fuel distribution, flow number, air side effective area, spray cone angle and spray SMD. The fuel used was aviation kerosine.

Apparatus for the relatively simple and rapid determination of the fuel distribution within the spray is also described.
501F Development Update
Authors: Entenmann D. T. , Hultgren K. G. , Smed J. P. , Aoyama K. , Tsukagoshi K. , Umemura S.
Published: March 2015

The 501F engine is a high temperature industrial grade 150MW size engine jointly developed by Westinghouse Electric Corporation and Mitsubishi Heavy Industries, LTD. Full load shop tests of the new engine were successfully completed at MHI’s Takasago Machinery Works in the summers of 1989 and 1991. Several design enhancements were incorporated into the engine through continuous development since the first test. The delivery schedule of the first engine provided the opportunity for the second full load shop test. This paper includes a discussion of those enhancements as well as discussions of the second full load shop test and plans for future development of the 501F engine.
Pin-Fin Heat Transfer: Contribution of the Wall and the Pin to the Overall Heat Transfer
Authors: Dabagh A. M. Ai , Andrews G. E.
Published: March 2015

The differences in the heat transfer coefficient between the pin and the wall in pin-fin heat transfer was determined for three pin length to diameter ratios. A staggered pin-fin array was used with a 50% duct flow blockage by the pins. The axial pitch-to-pin diameter ratio, X/D, was 1.5 and the transverse pitch-to-diameter ratio, S/D, was 2.0. Three pin length-to-diameter ratios, T/D, of 0.7. 1.0 and 2.2 were investigated. The mean heat transfer coefficient results were very similar to previous work for similar geometries. The axial variation of heat transfer coefficient showed this to be fairly uniform with a small peak at the fourth row. Around each pin four measurements of the heat transfer coefficients were made with four on the fin surface at each end. Thus 12 local heat transfer coefficients were made per pin-fin. These showed that for all three geometries the wall or fin heat transfer was always greater by 15–35% than the pin for the same velocity and Re.
An Experimental Investigation of Convective Heat Transfer at the Leading Edge of a Gas Turbine Airfoil
Authors: Gendron S. , Marchand N. J. , Korn C. , Immarigeon J. P. , Kacprzynski J. J.
Published: March 2015

This paper describes the experimental methods used to determine the surface temperatures and heat-transfer coefficients at the leading edge, and elsewhere over the surface, of a specially designed double-edge wedge shell specimen subjected to cyclic heating in a high velocity hot gas stream generated by a burner rig. The methods included temperature measurements with thermocouples (embedded below the surface) as well as surface temperature measurements by optical pyrometry. The experiments were carried-out at gas temperatures between 806 to 1323 °C and velocities in the range from Mach 0.32 to Mach 0.39. The calibration procedures for each method, the various testing conditions to which the airfoil-like specimen was exposed and the results pertaining to the determination of the surface temperatures and heat-transfer coefficients are described and discussed.
MTR390—Engine for the Future
Authors: Spirkl A. , Ducos J. S. , Thorn R.
Published: March 2015

The design of the MTF390, a turboshaft engine in the 1000 kw range, is based on proven technology and components developed well in advance of the actual programme start. The engine features a two stage centrifugal compressor, an annular reverse flow ring combustor, a single stage air cooled gas generator turbine, a two stage free power turbine, an integrated reduction and accessory gearbox with integral oil system. A full authority digital engine control provides the engine and system monitoring functions.

The development programme, which also includes a comprehensive integrated logistics support programme, is running according to schedule, more than 1400 engine hours have been logged including 200 flight hours with both a Flying Test Bed and the TIGER prototype helicopter.
Cold Flow Testing of the Space Shuttle Main Engine Alternate Turbopump Development High Pressure Fuel Turbine Model
Authors: Gaddis Stephen W. , Hudson Susan T. , Johnson P. Dean
Published: March 2015

The National Aeronautics and Space Administration’s (NASA’s) Marshall Space Flight Center (MSFC) has established a “cold” airflow turbine test program to experimentally determine the performance of liquid rocket engine turbopump drive turbines. Testing of the space shuttle main engine (SSME) alternate turbopump development (ATD) fuel turbine was conducted for “back-to-back” comparisons with the baseline SSME fuel turbine results obtained in the first quarter of 1991. Turbine performance, Reynolds number effects, and turbine diagnostics, such as stage reactions and exit swirl angles, were investigated at the turbine design point and at off-design conditions. The test data showed that the ATD fuel turbine test article was approximately 1.4 percent higher in efficiency and flowed 5.3 percent more than the baseline fuel turbine test article. This paper describes the method and results used to validate the ATD fuel turbine aerodynamic design. The results are being used to determine the ATD high pressure fuel turbopump (HPFTP) turbine performance over its operating range, anchor the SSME ATD steady-state performance model, and validate various prediction and design analyses.
Use of Subdomains for Inverse Problems in Branching Flow Passages
Authors: Krishnan S. , Agrawal Ajay K. , Yang Tah-teh
Published: March 2015

For inverse problems in complex flow passages, a calculation procedure based on multizone Navier-Stokes method was developed. A heuristic approach was employed to derive wall shape corrections from the wall pressure error. Only two subdomains sharing a row of control volumes were used in the present work. The grid work in the common region was identical for both subdomains. The flow solver, inverse calculation procedure, multizone Navier-Stokes method and subdomain inverse calculation procedure were validated independently against experimental data or numerical predictions. The subdomain inverse calculation method was applied to determine the wall shape of the main duct of a branching flow passage. This main duct was to minimize the pressure gradient downstream of the sidebranch. Inverse calculations resulted in a range of wall shapes with wall pressure distribution approaching the design (prescribed) wall pressure distribution. The present approach was illustrated for laminar, incompressible flows in branching passages. However, the method presented is flexible and can be extended for inverse turbulent flow calculations in multiply connected domains.
Numerical Simulation of Compressor Endwall and Casing Treatment Flow Phenomena
Authors: Crook A. J. , Greitzer E. M. , Tan C. S. , Adamczyk J. J.
Published: March 2015

A numerical study is presented of the flow in the endwall region of a compressor blade row, in conditions of operation with both smooth and grooved endwalls. The computations are first compared to velocity field measurements in a cantilevered stator/rotating hub configuration to confirm that the salient features are captured. Computations are then interrogated to examine the tip leakage flow structure since this is a dominant feature of the endwall region. In particular, the high blockage that can exist near the endwalls at the rear of a compressor blade passage appears to be directly linked to low total pressure fluid associated with the leakage flow. The fluid dynamic action of the grooved endwall, representative of the casing treatments that have been most successful in suppressing stall, is then simulated computationally and two principal effects are identified. One is suction of the low total pressure, high blockage fluid at the rear of the passage. The second is energizing of the tip leakage flow, most notably in the core of the leakage vortex, thereby suppressing the blockage at its source.
Viscous Throughflow Modelling for Multi-Stage Compressor Design
Authors: Howard M. A. , Gallimore S. J.
Published: March 2015

An existing throughflow method for axial compressors, which accounts for the effects of spanwise mixing using a turbulent diffusion model, has been extended to include the viscous shear force on the endwall. The use of a shear force, consistent with a no-slip condition, on the annulus walls in the throughflow calculations allows realistic predictions of the velocity and flow angle profiles near the endwalls. The annulus wall boundary layers are therefore incorporated directly in the throughflow prediction. This eliminates the need for empirical blockage factors or independent annulus boundary layer calculations.

The axisymmetric prediction can be further refined by specifying realistic spanwise variations of loss coefficient and deviation to model the three-dimensional endwall effects. The resulting throughflow calculation gives realistic predictions of flow properties across the whole span of a compressor. This is confirmed by comparison with measured data from both low and high speed multi-stage machines.

The viscous throughflow method has been incorporated into an axial compressor design system. The method predicts the meridional velocity defects in the endwall region and consequently blading can be designed which allows for the increased incidence, and low dynamic head, near to the annulus walls.
Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage
Authors: Green T. , Turner A. B.
Published: March 2015

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGV’s) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGV’s and rotor blades on the level of mainstream ingestion for different seal flow rates.

A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainsteam flow rates by controlling the rotor speed with an air brake.

The circumferential variation in hub static pressure was measured at the trailing edge of the NGV’s upstream of the seal gap and was found to significantly affect ingestion. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton 3D C.F.D. computer code was used to predict the smoothed time dependent pressure field for the rotor together with the pressure distribution downstream of the NGV’s.

The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace.

With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGV’s were found to significantly reduce mainstream ingestion seal flow rates, but a small level of ingestion existed even for very high levels of seal flow rate.
Three-Dimensional Navier-Stokes Computations of Transonic Fan Flow Using an Explicit Flow Solver and an Implicit κ–ϵ Solver
Authors: Jennions I. K. , Turner M. G.
Published: March 2015

Computational fluid dynamics (CFD) has become a powerful ally of the experimental test facility in revealing the flow physics of some highly complex flows. For certain classes of flow, CFD has reached maturity and is therefore being increasingly used in industry by designers. This paper is intended to show current transonic prediction capability at GE Aircraft Engines in terms of a recently developed 3D Navier-Stokes code. The flow simulations addressed are concerned with transonic fan design and illustrate those issues that are important to designers such as tip leakage flow, shock boundary layer interaction, boundary layer growth and account of internal solid bodies such as part-span shrouds and engine splitters. In this respect, three successively more complex Navier-Stokes simulations representative of modern fans: NASA Rotor 67, GE/Wennerstrom Rotor 4, and the GE/NASA E3 fan, are considered in this paper.
Ceramic Filters for Hot Gas Cleanup
Authors: White L. R. , Tompkins T. L. , Hsieh K. C. , Johnson D. D.
Published: March 2015

This paper reviews the properties of high temperature ceramic fibers and relates why strength, thermal shock resistance, chemical inertness, and high temperature capability are important properties for high temperature filter media. The use of candle filters, fabric filters, and composite filters will be discussed for removal of particulates from hot gas streams in electrical power generation systems, metal refining, chemical processing, and Diesel engine exhaust applications.
Utility Perspective of Selecting Air Filter for Simple-Cycle, Heavy-Duty Combustion Turbines
Authors: Lyons James W. , Morrison Alex
Published: March 2015

The combustion turbines evaluated for this study range in size (nominal) from 80 MW to 100 MW and operate at a compression ratio between 10 and 14. Under these conditions the compressor ingests about 500,000 to 725,000 cubic feet of air per minute for its rated output. With this volume of air, even low concentrations of contaminants can result in a significant total amount of contaminants entering the unit, which may cause compressor erosion, fouling, and foreign object damage in the compressor section and cooling air passage blockage, locking of turbine blade roots, and hot corrosion or sulfidation in the turbine section. Adequate protection against the above mentioned degradation or damage due to poor air quality may be obtained by using properly designed air filters. An inadequate filter system or having no filter system results in a reduction in power and efficiency over the life of the unit and may significantly decrease the intervals between maintenance and thereby increase the cost of maintenance. Consideration should be given to adding an air inlet filter when or after the combustion turbine without air filter is overhauled to reduce future maintenance costs.

This study investigates the need for an inlet air filtration system for the simple-cycle, heavy-duty combustion turbines from a cost/benefit and operation standpoint. Options for inlet air filters include a self-cleaning pulse type filter, a surface loading cartridge filter without pulse feature, and a three-stage depth loading type media type filter. Benefits are determined by estimates of improvements in performance and effects on the combustion turbine’s longevity and maintenance.
Use of Advanced CFD Codes in the Turbomachinery Design Process
Authors: Novak O. , Schäfer O. , Schönung B. , Pätzold H.
Published: March 2015

This paper describes the development and application of CFD codes, based on time-marching finite-volume formulations to the flow analysis in blade cascades, blade rows and stages of modern turbomachines. Special attention is paid to the reduction of the numerical dissipation of finite-volume discretization schemes, the numerical simulation of shock waves and to viscous effects. Furthermore, the application of solution-adaptive structured and unstructured computational grids is investigated. Finally, the ability of time-marching finite-volume methods to simulate three-dimensional flow effects in turbomachinery bladings is demonstrated.
A Conceptual Design for a Combined Cycle Power Plant Comprising Modified Exhaust-Heated Gas Turbine and a Steam Turbine Plant: Part I — Preliminary Calculations, Basic Dimensions and General Design Conception
Authors: Golinski Joseph A.
Published: March 2015

An example of the application of a modified exhaust -heated gas turbine system (with fourfold compression and fourfold expansion) coupled with a steam turbine plant with reheat has been presented. Schematic arrangement and design data of a combined plant have been shown (state parameters of fluids, mass-flow rates, dimensions, etc.). Natural gas has been taken into consideration as fuel. In spite of comparatively high pressure losses on the gas side a thermal efficiency of 50% on clutch (about 47,5% on terminals) is obtainable.
Durability Surveillance Program on the Advanced Gas Turbine GE Frame 7 F
Authors: Ondryas Igor S. , Meher-Homji Cyrus , Boehler Pierre , Dohner Clark
Published: March 2015

Worldwide pressures for reduction of power generation costs force the manufacturers of gas turbines to develop highly efficient units. Recent advances in the developments of high temperature materials coupled with advanced cooling techniques allow the developments of the new generation of advanced gas turbines with firing temperatures at 2300*F, which are being presently deployed in the marketplace. In order to establish a reference point regarding the durability of these machines, EPRI (Electric Power Research Institute) has launched a program to assess the durability of this new generation of advanced gas turbines. The first gas turbine to be observed is the General Electric MS 7001 F, located at the Potomac Electric Power Co. (PEPCO) Station H in Dickerson, Md. The Durability Surveillance Program shall be performed for 3 years during peaking operation (mostly summer and winter) beginning in May 1992 and continuing till 1995. Close observation of the gas turbine operation and maintenance, extensive monitoring of turbine operational parameters, detailed recording of performance and operational parameters and expanded inspection of the hot gas path hardware are the main activities in this Durability Surveillance program. Similar test programs are planned for the Westinghouse 501 F gas turbine and the GE MS 7001 FA gas turbine. The results of these tests shall be available to EPRI member utilities and other advanced gas turbine users.
Some Basic Reflections About the Influence of Non-Metallic Inclusions on Rolling Contact Fatigue of Bearing Steels
Authors: Böhmer Hans-Jürgen
Published: March 2015

The detrimental influence of inclusions on rolling contact fatigue behaviour of bearing steel is well known and empirically described. Yet only a few publications exist where the effect of inclusions is investigated analytically. This paper presents a new method to describe the influence of inclusions based on a mechanical analysis.

From this analysis some general effects of inclusions on material stress and behaviour in rolling contact fatigue were concluded. The actual “notch effect” of inclusions is qualitatively independent on their specific properties, even if they are more pliable or stiffer than the matrix. Only the amount of the notch effect is — to a certain extent — dependent on their respective properties. Many discrepancies between classical theory of Hertzian contact and damage analysis of rolling element bearings can be explained by this analysis.

The correct appraise of compressive residual stresses in rolling contact fatigue is strongly bound to the consideration of inclusions. It is shown that compressive residual stresses have the greatest benefit if they are about 15% of the applied Hertzian pressure. Exceeding this value may be detrimental.
Separated Flow in a Low Speed Two-Dimensional Cascade: Part I — Flow Visualization and Time-Mean Velocity Measurements
Authors: Yocum Adam M. , O’Brien Walter F.
Published: March 2015

This study was conducted for the purpose of providing a more fundamental understanding of separated flow in cascades and to provide performance data for fully-stalled blade rows. Cascades of a single blade geometry and a solidity of unity were studied for three stagger angles and the full range of angle of attack, extending well into the stalled flow regime. Results are presented from flow visualization and time-mean velocity measurements of stalled flow in the cascade. Surface and smoke flow visualization revealed that the blade stagger angle is a key parameter in determining the location of the separation line and the occurrence of propagating stall. Time-mean velocity measurements obtained with a dual hot split-film probe also showed that the separated velocity profiles within the blade passages and the profiles in the wake have distinctly different characteristics depending on the stagger angle.
Radial Transport and Momentum Exchange in an Axial Compressor
Authors: Dring Robert P.
Published: March 2015

The objective of this work was to examine radial transport in axial compressors from two perspectives. The first was to compare the mixing coefficient based on a secondary flow model (using measured radial velocities) with that based on a turbulent diffusion model. The second was to use measured airfoil pressure forces and momentum changes to assess the validity of the assumption of diffusive radial transport which is common to both models. These examinations were carried out at both design and off-design conditions as well as for two rotor tip clearances. In general it was seen that radial mixing was strongest near the hub and that it increased dramatically at near-stall conditions. It was also seen that radial transport could cause large differences (≈ 100%) between the force on an airfoil and the change in momentum across the airfoil at the same spanwise location.
Prescribed-Curvature-Distribution Airfoils for the Preliminary Geometric Design of Axial-Turbomachinery Cascades
Authors: Korakianitis Theodosios
Published: March 2015

Blade surfaces with continuous curvature and continuous slope of curvature minimize the possibility of flow separation, lead to improved blade designs, and reduce the direct and inverse blade-design iterations for the selection of isolated airfoils and gas-turbine-blade cascades. A method for generating two-dimensional blade shapes is presented. The geometry near the trailing edge is specified by an analytic polynomial, the main portion of the blade surface is mapped using as input a prescribed surface-curvature distribution, and the leading edge is specified as a thickness distribution added to a construction line. This procedure is similar for the suction and pressure surfaces, and by specification it constructs continuous slope-of-curvature surfaces that result in smooth surface-Mach-number and surface-pressure distributions. The method can be used to generate subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The resulting geometric shapes can be used as inputs to various blade-design sequences. It is shown that, with other cascade-design parameters being equal, increasing the stagger angle of turbine blades results in more-front-loaded and thinner blades, and that there is an optimum stagger angle resulting in minimum wake thickness. The subsonic axial-turbine blade rows included for discussion in this paper have been designed by iterative modifications of the blade geometry to obtain a desirable velocity distribution. The blade-design method can be used to improve the aerodynamic and heat transfer performance of turbine cascades, and it can result in high-performance airfoils, even if using the direct method exclusively, in very few iterations.
Erosion Characteristics of Ceramic Particulate and Whisker Reinforced Aluminum Composites
Authors: Gupta Suresh
Published: March 2015

Advanced composite materials are one of the key enabling technologies for achieving the planned revolutionary improvements in the next generation of aero gas turbine engines. For example the thrust to weight ratio of advanced military engines is targeted to double (to 20:1) within the next 10 to 15 years. A number of families of advanced composites are being developed, and metal matrix composites is one significant member of these. These can be either ceramic fiber or ceramic particulate/whiskers embedded in matrixes of aluminum, titanium or superalloys. Silicon carbide particulate/whisker reinforced aluminum has been under consideration for the cold section of front end engine components such as compressor blades, compressor stator vanes and casings. One potentially serious problem anticipated in using these composites for such application is its behavior in particulate erosion, as may happen in sandy environments and runways. This paper describes the test program undertaken to study this problem, and discusses the results obtained. It was found that the erosion rate of such composites can be considerably higher than that of non-reinforced aluminum alloys. Further, the characteristic erosion behavior is modified significantly. Also identified were new mechanisms of material removal coming into play. These are also discussed.
The Effects of Incident Turbulence and Moving Wakes on Laminar Heat Transfer in Gas Turbines
Authors: Dullenkopf K. , Mayle R. E.
Published: March 2015

The effect of free-stream turbulence and moving wakes on augmenting heat transfer in accelerating laminar boundary layers is considered. First, the the effect of free-stream turbulence is re-examined in terms of a Nusselt number and turbulence parameter which correctly account for the free-stream acceleration and a correlation for both cylinders in cross flow and airfoils with regions of constant acceleration is obtained. This correlation is then used in a simple quasi-steady model to predict the effect of periodically passing wakes on airfoil laminar heat transfer. A comparison of the predictions with measurements shows good agreement.
Effects of Free-Stream Turbulence and Adverse Pressure Gradients on Boundary Layer Transition
Authors: Gostelow J. P. , Blunden A. R. , Walker G. J.
Published: March 2015

Boundary layer measurements are presented through transition for six different free-stream turbulence levels and a complete range of adverse pressure gradients for attached laminar flow.

Measured intermittency distributions provide an excellent similarity basis for characterizing the transition process under all conditions tested when the Narasimha procedure for determining transition inception is used. This inception location procedure brings consistency to the data.

Velocity profiles and integral parameters are influenced by turbulence level and pressure gradient and do not provide a consistent basis. Under strong adverse pressure gradients transition occurs rapidly and the velocity profile has not fully responded before the completion of transition. The starting turbulent layer does not attain an equilibrium velocity profile.

A change in pressure gradient from zero to even a modest adverse level is accompanied by a severe reduction in transition length. Under diffusing conditions the physics of the transition process changes and the spot formation rate increases rapidly; instead of the “breakdown in sets” regime experienced in the absence of a pressure gradient, transition under strong adverse pressure gradients is more related to the amplification and subsequent instability of the Tollmien-Schlichting waves. Measurements reveal an exponential decrease in transition length with increasing adverse pressure gradient; a less severe exponential decrease is experienced with increasing turbulence level. Correlations of transition length are provided which facilitate its prediction in the form of suitable length parameters including spot formation rate.
ATTAP Ceramic Gas Turbine Technology Development
Authors: Smyth J. R. , Morey R. E.
Published: March 2015

In the Advanced Turbine Technology Applications Project (ATTAP), Garrett Auxiliary Power Division (GAPD) continues to address critical technologies for the application of ceramics in gas turbine engines. Design methods and component and fabrication development are culminating in rig and engine testing to confirm ceramic technology development. Analytical methods for designing impact-resistant ceramic engine components have been verified in experiments, and improved regenerator seals and combustor designs have been tested. Engineered process development by selected subcontractors has resulted in delivery of high-quality ceramic components. All of these efforts are aimed at a planned all-ceramic turbine engine demonstration for 300 hours operation up to 2500F (1371C).

ATTAP is a continuing program funded by the U.S. Department of Energy (DOE) Office of Transportation Technologies and administered by the NASA-Lewis Engineering Research Center under Contract No. DEN3-335.
An Externally Pressurized Air Bearing System, Journals and Thrust, for Application to Small Turbomachinery
Authors: Turner A. B. , Davies S. J. , Nimir Y. L. , Richardson J. D.
Published: March 2015

An aerostatic (externally pressurized) air bearing system for application to small high speed, low temperature turbomachinery has been designed and successfully tested at over 100,000 rpm using an air supply at a gauge pressure of 3.4 bar (50 psig).

The test rig used a Holset turbocharger centrifugal compressor impeller and radial turbine wheel mounted at either end of a 150 mm long 40 mm diameter shaft with two 23 mm long inboard journal bearings mounted on either side of an integral 100 mm diameter tapered thrust collar. The turbine was driven by an independent air supply with a maximum temperature of 200°C, and the unit was operated with the shaft vertical. A static axial thrust capability of over 1000 N (225 lbf) has been demonstrated using a novel plenum chamber arrangement to overcome pneumatic instability (air hammer) problems. The paper presents details of the design, some static rig tests and the dynamic test conditions and results.
Ceramic Component Reliability With the Restructured NASA/CARES Computer Program
Authors: Powers Lynn M. , Starlinger Alois , Gyekenyesi John P.
Published: March 2015

The Ceramics Analysis and Reliability Evaluation of Structures (CARES) integrated design program on statistical fast fracture reliability of monolithic ceramic components is enhanced to include the use of a neutral data base, two-dimensional modeling and variable problem size. The data base allows for the efficient transfer of element stresses, temperatures and volumes/areas from the finite element output to the reliability analysis program. Elements are divided to insure a direct correspondence between the subelements and the Gaussian integration points. Two-dimensional modeling is accomplished by assessing the volume flaw reliability with shell elements. To demonstrate the improvements in the algorithm, example problems are selected from a round-robin conducted by WELFEP (WEakest Link failure probability prediction by Finite Element Postprocessors).
Evaluation of Fast Fracture Strength of Ceramic Components Under Multiaxial Stress States
Authors: Uchimura H. , Kokaji A. , Kaji M.
Published: March 2015

Several fracture criteria were studied under multiaxial stress states by Matsuo’s multiaxial fracture probability distribution function including effects of both volume and surface cracks. Tested material was a pressureless-sintered silicon nitride. Tensile (compressive)-torsional tests revealed that experimental data were satisfactorily described by Shitty’s empirical criterion for C=1.46. Good agreements for a spin and a thermal shock tests were obtained applying the Weibull parameters and the Shetty’s parameter.
Improving Dynamic Response of a Single-Spool Gas Turbine Engine Using a Nonlinear Contoller
Authors: Qi O. F. , Maccallum N. R. L. , Gawthrop P. J.
Published: March 2015

This paper describes the design of a closed-loop nonlinear controller to improve the dynamic response of a single-spool gas turbine engine. The nonlinear controller is obtained by scheduling the gains of multivariable compensators as a function of engine non-dimensional shaft speed. The compensators, whose outputs are fuel flow and nozzle area, are designed using optimal control theory based on a set of linear models generated from a nonlinear engine simulation. Investigations are also made into developing simple algorithms to obtain an analytical expression for the compressor given its characteristic. The detailed process of developing a nonlinear simulation model for the engine is also described. The open-loop fuel controller is studied using the digital simulation.
Modelling and Analysis of Gas Turbine Performance Deterioration
Authors: Lakshminarasimha A. N. , Boyce M. P. , Meher-Homji C. B.
Published: March 2015

The effects of performance deterioration in both land and aircraft gas turbines are presented in this paper. Models for two of the most common causes of deterioration viz. fouling and deterioration are presented. A stage stacking procedure which uses new installed engine field data for compressor map development is described. The results of the effect of fouling in a powerplant gas turbine and that of erosion in a aircraft gas turbine are presented. Also described are methods of fault threshold quantification and fault matrix simulation. Results of the analyses were found to be consistent with field observations.
Aircraft Engine Integration for the M88-RAFALE Couple
Authors: Ramette Philippe , Corde Jean Christophe
Published: March 2015

As all other comparable programs, the couple RAFALE-M88 has to be a fully optimized multirole weapon system with the highest level of integration; a key factor for that purpose is the very good prebuilt integration of the engine within the aircraft.

After a short description of the main historical milestones of the aircraft and engine programs development and integration, the paper will first summarize the rigourous procedures which are used by aircraft and engine manufacturers, official services and future Air Force and Navy users.

Then, the paper will detail the main points where aircraft engine integration as to be lead precisely and carefully; these points are:

-at first, the electronical links which are establised between the aircraft and the engine, due to the high complexity of flight softwares who have to work and talk with each others;

-secondly, the aerodynamical subjects, including air intake and exhaust nozzle installation;

-thirdly, the mechanical integration (geometry, mechanical behaviour, …);

-then all kinds of fluid circuits or equiments.
Textron Lycoming AGT1500 Engine Operational and Support Cost Reduction
Authors: Pellegrino Edward
Published: March 2015

An aggressive program to significantly reduce the sustainment cost of the M1 Abrams Main Battle Tank Powertrain was initiated by the Army Material Command (AMC) in 1985. The powerpack (engine and transmission) sustainment cost had been calculated by the Army to be twenty-one percent (21%) of the total M1 sustainment cost with the engine accounting for fourteen percent (14%) of the total. Although this figure was considerably less than the original assumption of thirty percent (30%) for the engine alone, the cost was considered significant.

In order to achieve the Army mandated fifty percent (50%) savings on sustainment cost, Textron Lycoming pursued an aggressive reliability improvement program recognizing the potential to increase operational readiness while decreasing future operational and support cost. A major milestone was achieved by 1988 when the powerpack sustainment cost was calculated to be ten percent (10%) of the total M1 sustainment cost.

In 1989, a study conducted by Textron Lycoming concluded that additional and substantial operational and support cost reductions could be realized by addressing and improving the engine’s field maintenance concept and its application.
Aircraft Turbine Engine NOx Emission Limits: Status and Trends
Authors: Bahr D. W.
Published: March 2015

Within recent years, the NOx emissions of aircraft engines have received increased attention. More stringent limits on the NOx emissions of future subsonic civil aircraft engines are being considered. A 20 percent increase in the stringency of the existing ICAO standard has been proposed and, for the longer-term, the possibility of further increased stringency is being studied. For future supersonic civil aircraft engines, very stringent goals have been established. To meet these goals, combustor designs with ultralow NOx levels are required. Extensive efforts are, therefore, underway to develop low NOx combustors for use in future generations of both subsonic and supersonic aircraft engines.
Gas Turbine Driving Reciprocating Compressors Experience in Natural Gas Applications
Authors: Giacomelli E. , Petrini P. , Montelatici A. , Desolati M.
Published: March 2015

The flexibility of reciprocating compressors combined with the utilization of variable speed drives like gas turbines optimizes operating and capital investment costs in natural gas services. Reliability and respect for limits specified in pollution control regulations are the most significant requirements related to modern compression stations. Equipped with monitoring systems, the trains must benefit by special design procedures and modern full-load test facilities to ensure the complete confidence of users.

The above features, together with energy saving advantages, make it possible to forecast the increasing application of compressor - turbine arrangements.
Smart Monitoring for Compressor Stations
Authors: Van Hardeveld Thomas
Published: March 2015

A major remaining way to improve operational effectiveness for compressor stations is by the combination of on-line monitoring and enhanced diagnostics which can be described by the general term ‘smart monitoring’. The introduction of smart monitoring techniques will allow unattended operation of equipment to a greater extent than has been possible so far with remote access to the monitoring and diagnostic information from remote field, maintenance, and gas control locations. On-site attendance by operating and maintenance personnel can then be limited to responding to unscheduled events and for doing routine and scheduled maintenance. The role of enhanced diagnostics in this context is to anticipate undesirable operating conditions (and possibly mitigate or avoid them by certain control actions), to obtain earlier prediction of equipment deterioration or potential failures, to carry out a detailed analysis of unscheduled events and shutdowns, and to enable a high level of on-condition maintenance. The function of the intelligent diagnostics is to convert monitoring data, which can be voluminous with online monitoring, into a reduced subset of relevant information which is needed to make decisions. In this paper, a conceptual approach to smart monitoring is described and initial results of an on-site prototype are presented. Future implementation issues are also discussed.
Inverse Design of Compressor and Turbine Blades at Transonic Flow Conditions
Authors: Léonard O. , Van den Braembussche R. A.
Published: March 2015

This paper describes the design of realistic blade shapes using an inverse method. Special attention is given to the geometrical and mechanical constraints imposed upon the blade.

Examples presented in this paper illustrate how a better understanding of the theoretical relations between imposed velocity and resulting geometry can help satisfy the geometrical restrictions. Another method using a numerical procedure for finding a compromise between the target velocity distribution and geometrical restrictions is also proposed and illustrated by an example.

A blade design procedure using an inviscid inverse method and a boundary layer calculation method is described and applied to the design of a shock free transonic compressor cascade. The iterative character of the procedure provides a blade shape control good enough to design sufficiently thick blades resulting in realistic geometries. The blade shape coordinates are given as a possible bench mark for inviscid or viscous two-dimensional methods.