bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Incident Wake Conditions on the Mean Heat Transfer of an Airfoil
Authors: Dullenkopf K. , Schulz A. , Wittig S.
Published: March 2015

The flow phenomena of wakes shed by upstream blade rows is a well–known problem in turbomachinery which influences blade forces, vibrations, losses and heat transfer. With respect to the heat load to turbine blades this problem becomes even more complex because of the interaction between wake, potential flow and the boundary layer along the surface of the airfoil.

Experimentally evaluated mean heat-transfer coefficients obtained under different unsteady initial conditions are reported. The heat–transfer measurements have been carried out in the cascade test facility at the ITS in Karlsruhe using a rotating bar wake generator placed upstream of the cascade to simulate the wake passing process. The variation of the wake parameters includes different wake passing frequencies, cascade inlet Reynolds numbers and wake inclination angles. In addition, the relevant parameters of the unsteady wake have been measured by means of a fixed hot–wire anemometer using the ensemble average technique. The results are compared to those from the literature for the wake of a cylinder in cross–flow. They also serve as experimental base for parallel theoretical analyses.
Active Stabilization of Centrifugal Compressor Surge
Authors: Pinsley J. E. , Guenette G. R. , Epstein A. H. , Greitzer E. M.
Published: March 2015

Active suppression of centrifugal compressor surge has been demonstrated on a centrifugal compressor equipped with a servo-actuated plenum exit throttle controller. The control scheme is fundamentally different from conventional surge control techniques in that it addresses directly the dynamic behavior of the compression system to displace the surge line to lower mass flows. The method used is to feed back perturbations in plenum pressure rise, in real time, to a fast acting control valve. The increased aerodynamic damping of incipient oscillations due to the resulting valve motion allows stable operation past the normal surge line. For the compressor used, a 25% reduction in the surge point mass flow was achieved, over a range of speeds and pressure ratios. Time-resolved measurements during controlled operation revealed that the throttle required relatively little power to suppress the surge oscillations, because the disturbances are attacked in their initial stages. Although designed for operation with small disturbances, the controller was also able to eliminate existing, large amplitude, surge oscillations. Comparison of experimental results with theoretical predictions showed that a lumped parameter model appeared adequate to represent the behavior of the compression system with the throttle controller and, perhaps more importantly, to be used in the design of more sophisticated control strategies.
Centrifugal Compressor Impeller Aerodynamics: An Experimental Investigation
Authors: Joslyn H. David , Brasz Joost J. , Dring Robert P.
Published: March 2015

The ability to acquire blade loadings (surface pressure distributions) and surface flow visualization on an unshrouded centrifugal compressor impeller is demonstrated. Circumferential and streamwise static pressure distributions acquired on the stationary shroud are also presented. Data was acquired in a new facility designed for centrifugal compressor aerodynamic research. Blade loadings calculated with a blade–to–blade potential flow analysis are compared with the measured results. Surface flow visualization reveals some complex aspects of the flow on the surface of the impeller blading and hub. In a companion paper, Dorney and Davis (1990), a state–of–the–art, three–dimensional, time–accurate, Navier Stokes prediction of the flow through the impeller is presented.
Similarity Behavior in Transitional Boundary Layers Over a Range of Adverse Pressure Gradients and Turbulence Levels
Authors: Gostelow J. P. , Walker G. J.
Published: March 2015

Boundary layer transition has been investigated experimentally under low, moderate and high free-stream turbulence levels and varying adverse pressure gradients. Under high turbulence levels and adverse pressure gradients a pronounced subtransition was present. A strong degree of similarity in intermittency distributions was observed, for all conditions, when the Narasimha procedure for determination of transition inception was used.

Effects of free-stream turbulence on the velocity profile are particularly strong for the laminar boundary layer upstream of the transition region. This could reflect the influence of the turbulence on the shear stress distribution throughout the layer and this matter needs further attention. The velocity profiles in wall coordinates undershoot the turbulent wall layer asymptote near the wall over most of the transition region.

The rapidity with which transition occurs under adverse pressure gradients produces strong lag effects on the velocity profile; the starting turbulent boundary layer velocity profile may depart significantly from local equilibrium conditions. The practice of deriving integral properties and skin friction for transitional boundary layers by a linear combination of laminar and turbulent values for equilibrium layers is inconsistent with the observed lag effects.

The velocity profile responds sufficiently slowly to the perturbation imposed by transition that much of the anticipated drop in form factor will not have occurred prior to the completion of transition. This calls into question both experimental techniques which rely on measured form factor to characterize transition and boundary layer calculations which rely on local equilibrium assumptions in the vicinity of transition.
A Numerical Study of the Influence of Disc Geometry on the Flow and Heat Transfer in a Rotating Cavity
Authors: Lapworth B. L. , Chew J. W.
Published: March 2015

Numerical solutions of the Reynolds-averaged Navier-Stokes equations have been used to model the influence of cobs and a bolt cover on the flow and heat transfer in a rotating cavity with an imposed radial outflow of air. Axisymmetric turbulent flow is assumed using a mixing length turbulence model. Calculations for the non-plane discs are compared with plane disc calculations and also with the available experimental data. The calculated flow structures show good agreement with the experimentally observed trends. For the cobbed and plane discs, Nusselt numbers are calculated for a combination of flow rates and rotational speeds; these show some discrepancies with the experiments, although the calculations exhibit the more consistent trend. Further calculations indicate that differences in thermal boundary conditions have a greater influence on Nusselt number than differences in disc geometry. The influence of the bolt cover on the heat transfer has also been modelled, although comparative measurements are not available.
Heat Transfer Measurements in Rectangular Channels With Orthogonal Mode Rotation
Authors: Morris W. D. , Ghavami-Nasr G.
Published: March 2015

The influence of rotation on local heat transfer in a rectangular-sectioned duct has been experimentally studied for the case where the ductrotates about an axis orthogonal to its own central axis. The coolant used was air with the flow direction in the radially outwards direction. This rotating flow geometry is encountered in the internal cooling of gas turbine rotor blades.
The Role of Primary Jets in the Dome Region Aerodynamics of a Model Can Combustor
Authors: Richards C. D. , Samuelsen G. S.
Published: March 2015

The role of the primary jets in the aerothermal behavior and overall performance of a gas turbine combustor is explored through an experimental study. The study is performed in a model laboratory combustor that possesses the essential features of practical combustors. The test bed is designed to accommodate optical access for laser diagnostics and overall flow visualization, and is capable of incorporating variable inlet geometries. In the present case, the combustor is operated on JP-4 at atmospheric pressure. A parametric variation in the number of jets per row and axial location of the jet row is performed. The aerodynamic and thermal fields are characterized using laser anemometry and a thermocouple probe respectively. Species concentrations are acquired via extractive probe sampling. The results demonstrate the importance of primary jet location with respect to the dome swirler. The percent mass recirculated into the dome region, as well as the overall uniformity of mixing and combustion efficiency, are substantially influenced by jet row location. The momentum ratio of the incoming primary jet stream to that of the approaching crossflow of reacting dome gases has a direct impact on the mixing patterns as well. An increase in the number of primary jets leads, in the present case, to more uniform mixing.
The Influence of Inlet Swirl Distortions on the Performance of a Jet Propulsion Two-Stage Axial Compressor
Authors: Pazur Wolfram , Fottner Leonhard
Published: March 2015

Aeroengine intakes containing S-shaped diffusers produce different types of inlet swirl distortions and essentially a combination of a twin swirl and a bulk swirl. The main object of this investigation was to assess the influence of inlet swirl distortions on the performance of a transonic two-stage axial compressor installed in a turbo jet bypass engine Larzac 04. A typical inlet swirl distortion was simulated by a delta-wing in front of the engine. An experimental method was investigated to measure the performance map of the installed low pressure compressor for different engine operating lines. The influence of an inlet swirl distortion with different strengths on the performance map of the compressor was investigated experimentally. It is shown that the performance parameters decrease and a temperature distortion is generated behind the compressor. As the basis of the theoretical investigations of the performance map including inlet swirl distortions a computing model considering four compressors working in parallel was established. The model is based on the idea that an inlet swirl distortion can be substituted by two fundamental types of swirl components, i.e. a bulk swirl co-rotating, and a bulk swirl counter-rotating to the revolution of the compressor. Computed performance maps of the compressor will be discussed and compared with the experimental data.
On the Leading Edge: Combining Maturity and Advanced Technology on the F404 Turbofan Engine
Authors: Powel S. F.
Published: March 2015

The overall design concept of the F404 afterburning turbofan engine is reviewed together with some of the lessons learned from over 2 million flight hours in service. GE Aircraft Engines’ derivative and growth plans for the F404 family are then reviewed including the “Building Block” component development approach. Examples of advanced technologies under development for introduction into new F404 derivative engine models are presented in the areas of materials, digital and fiber optic controls systems, and vectoring exhaust nozzles. The design concept and details of the F404-GE-402, F412-GE-400 and other derivative engines under full scale development are described. Studies for future growth variants and the benefits of the F404 derivative approach to development of afterburning engines in the 18–24,000 pounds (80–107 kN) thrust class and non-afterburning engines in the 12–19,000 pounds (53–85 kN) class are discussed.
Similarity Analysis of Compressor Tip Clearance Flow Structure
Authors: Chen G. T. , Greitzer E. M. , Tan C. S. , Marble F. E.
Published: March 2015

A new approach is presented for analyzing compressor tip clearance flow. The basic idea is that the clearance velocity field can be (approximately) decomposed into independent through-flow and cross-flow, since chordwise pressure gradients are much smaller than normal pressure gradients in the clearance region. As in the slender body approximation in external aerodynamics, this description implies that the three-dimensional, steady, clearance flow can be viewed as a two-dimensional, unsteady flow. Using this approach, a similarity scaling for the cross-flow in the clearance region is developed and a generalized description of the clearance vortex is derived. Calculations based on the similarity scaling agree well with a wide range of experimental data in regard to flow features such as cross-flow velocity field, static pressure field, and tip clearance vortex trajectory. The scaling rules also provide a useful way of exploring the parametric dependence of the vortex trajectory and strength for a given blade row. The emphasis of the approach is on the vortical structure associated with the tip clearance because this appears to be a dominant feature of the endwall flow; it is also shown that this emphasis gives considerable physical insight into overall features seen in the data.
Essential Ingredients for the Computation of Steady and Unsteady Blade Boundary Layers
Authors: Jang H. M. , Platzer M. F. , Ekaterinaris J. A. , Cebeci T.
Published: March 2015

Two methods are described for calculating pressure distributions and boundary layers on blades subjected to low Reynolds numbers and ramp–type motion. The first is based on an interactive scheme in which the inviscid flow is computed by a panel method and the boundary layer flow by an inverse method that makes use of the Hilbert integral to couple the solutions of the inviscid and viscous flow equations. The second method is based on the solution of the compressible Navier–Stokes equations with an embedded grid technique that permits accurate calculation of boundary layer flows. Studies for the Eppler and NACA–0012 airfoils indicate that both methods can be used to calculate the behavior of unsteady blade boundary layers at low Reynolds numbers provided that the location of transition is computed with the en–method and the transitional region is modelled properly.
Secondary Flow and Loss Distribution in a Radial Compressor With Untwisted Backswept Vanes
Authors: Sipos G.
Published: March 2015

The unshrouded impeller and the vaneless diffuser of a single-stage radial compressor have been investigated at three flow rates. Three-dimensional velocities and pressures were measured at a tip speed of 84 m/s by an L2F-velocimeter, a slanted single hot-wire probe and piezoresistive pressure transducers. The measurements show that upstream the blading the averaged meridional inlet flow angle is about 54 degree and a periodical variation of the meridional flow angle of about 25 degree occurs near the casing wall. Further, an inlet vortex of clockwise direction appears and an initial whirl is induced. The specific work of the initial whirl corresponds to approximately 12% of the enthalpy losses between inlet pipe and diffuser outlet. In the beginning of the passage, the inlet vortex is suppressed and a solid body vortex of counterclockwise direction can be observed. At the outlet, a heavy flow deceleration at the blade suction side with subsequent separation can be seen. Increasing the flow rate decreases the wake and causes a more uniform loss distribution in this area. The measured secondary vortex flow and rotary stagnation pressure gradients are compared with test results from impellers with inducer. The incidence of the investigated impeller is greater than that of the impellers with inducer, but the wake-jet outlet flows are very similar. Inlet losses could be reduced by improving incidence angles by matching the blade angles to the inlet flow angles. Smaller blade angles at the shroud would reduce or eliminate separation at the leading edge, and the resulting reduction in low momentum fluid along the suction surface would help to avoid separation on that surface near the outlet.
Second-Law Analysis of Fluidized-Bed Steam Generators
Authors: Bidini Gianni , Grimaldi Carlo N. , Manfrida Giampaolo
Published: March 2015

Direct and indirect exergy balances are applied to a simplified fluidized bed combustor. The major losses are calculated, including exergy from chemical reactions (combustion, calcination, and sulfation), heat transfer, and sensible heat release to the environment (ash and solid residue flows). The analysis is applied to atmospheric and pressurized fluidized bed combustors.
Stealth Aircraft-History, Technology and Outlook
Authors: Sweetman Bill
Published: March 2015

The development of low observables or Stealth technology is reviewed. Brief descriptions are given of the major Stealth aircraft programs now under way, including the Lockheed F-117A, the Northrop B-2, the US Air Force’s Advanced Tactical Fighter and the US Navy’s A-12. Mention is made of LO work in other nations and potential counters to Stealth are summarised.
Flight Development of the RTM 322 Engine
Authors: Sewell Peter , Scears Paul E.
Published: March 2015

The RTM 322 engine, under development by Rolls-Royce Turbomeca Ltd, is a viable candidate engine for future incorporation in S-70, H-60, EH101 and NH90 helicopters. An important ingredient in the development of the engine is its flight testing, currently being carried out in a Sikorsky S-70C (Civil version of the U S Army UH60 BLACK HAWK). This has not only served realistically to uncover and correct at very early stages those types of problem common to the development of all new engines but has also equally afforded an early look at installation, control and engine/airframe dynamic characteristics which, of course, will simplify later Production Series incorporation.

A brief description of the RTM 322 engine design and its development status is given followed by a summary of the installation and flight testing in the S-70C. Ground and flight test results in the S-70C are discussed and data and photographs presented.
Development of Corrosion Resistant Coatings for Marine Gas Turbine Applications
Authors: Nagaraj B. A. , Wortman D. J. , Maricocchi A. F. , Patton J. S. , Clarke R. L.
Published: March 2015

The performance of a number of selected diffusion and overlay coatings was evaluated using an atmospheric pressure burner rig; the test environment contained compounds of vanadium, sodium and sulfur. The tests were designed to simulate the deposit chemistry and sulfur trioxide partial pressures expected in a marine gas turbine engine operating on contaminated fuel. The tests were performed for up to 1000 hours at 1300°F and 1650°F. At 1650°F, virtually all the coatings tested were severely corroded, emphasizing the necessity of improved coating materials such as ceramics to resist vanadic corrosion. At 1300°F, FeCrAlY, pack chromide and CoCrAlY coatings with high chromium performed well.

Yttria stabilized zirconia coatings, with selected bond coats, were evaluated with fuels containing low (0.3ppm) and high (21ppm) concentrations of vanadium in atmospheric burner rig at 1650°F. Reaction products, primarily yttrium vanadate, were observed in both tests. The results are discussed in terms of bond coat corrosion and chemistry of the test environment.
Garrett’s Turboshaft Engines and Technologies for the 1990s
Authors: Pyle Terry , Aldrich Dan
Published: March 2015

Garrett Engine Division of Allied-Signal Aerospace, Inc., which supplies small-to-medium size gas turbine propulsion engines to the fixed-wing aviation market, is expanding its product line to include the small-to-medium turboshaft engine for the rotary wing (helicopter) aviation market. The recent win of the T800-LHT-800 down-select formed a firm foundation for this expansion. Garrett is developing the T800 in a partnership with the Allison Gas Turbine Division of General Motors Corporation, under the company name of Light Helicopter Turbine Engine Company (LHTEC). The T800 turboshaft engine (1300-shp, 1000-kW class), which has superior performance in this power class (10 to 30 percent better specific fuel consumption and power-to-weight than current production turboshaft engines), is designed to power the U.S. Army’s LHX light attack helicopter. Garrett is pursuing complementary technologies focused on serving a full spectrum of turboshaft engine requirements for the 1990s and beyond. Garrett is also teamed with General Electric Aircraft Engines (GEAE), for the Joint Turbine Advanced Gas Generator (JTAGG) demonstrator program. JTAGG supports the Integrated High Performance Turbine Engine Technology (IHPTET) initiative of doubling propulsion system capabilities by the year 2003. New technologies incorporated in the T800, and emerging technologies and concepts applicable to future turboshafts, are discussed.
Analytical Statistics of Forced Response of a Mistuned Bladed Disk Assembly in Subsonic Flow
Authors: Chen S. , Sinha A.
Published: March 2015

The statistics of the forced response of a structurally and aerodynamically coupled bladed disk assembly have been computed efficiently by the analytical technique. The validity of the analytical technique has been corroborated by comparison with the results from numerical simulations. Lastly, the effects of the following parameters on the statistics of the maximum amplitude have been studied: aerodynamic coupling, fluid density, and stagger angle.
An Experimental Investigation of Loss Reduction With Riblets on Cascade Blade Surfaces and Isolated Airfoils
Authors: Fang Chen , Yan-Ping Tang , Mao-Zhang Chen
Published: March 2015

Experimental investigations of loss reduction with riblets have been made. Riblets were put on the blade surfaces in different ways in a compressor cascade or on an isolated airfoil. More than 8% drag reduction benefits for an isolated airfoil and more than 10% loss reduction benefits for the compressor cascade have been obtained by using riblets only on blade pressure surfaces rather than on both pressure and suction surfaces. The mechanism underlying these results has been discussed.
Measured and Predicted Effects of Inlet Distortion on Axial Compressors
Authors: Longley J. P.
Published: March 2015

Encouraging developments have recently been made both in the understanding and the modelling of compressor flowfields. This paper describes an experimental investigation undertaken to assess the validity of the assumptions made in the simple non-linear model for a bladerow operating in an unsteady or non-uniform flowfield. The results show that the basic fluid dynamics of the problem have been correctly modelled and that meaningful predictions may be made. The measurements also indicate that inlet guide vanes may be more sensitive to incidence variations than had been previously thought. The effects of inter-bladerow gaps are also discussed.
Flow Visualization in a Simulated Brush Seal
Authors: Braun M. J. , Hendricks R. C. , Canacci V.
Published: March 2015

A method to visualize and characterize the complex flow fields in simulated brush seals is presented. The brush seal configuration was tested in a water and then in an oil tunnel. The visualization procedure revealed typical regions that are rivering, jetting, vortical or lateral flows and exist upstream, downstream or within the seal. Such flows are engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability.

While the effects of interface motion for linear or cylindrical configurations have not been considered herein, it is believed that the observed flow fields characterize flow phenomenology in both circular and linear brush seals. The axial pressure profiles upstream, across and downstream of the brush in the oil tunnel have been measured under a variety of inlet pressure conditions and the ensuing pressure maps are presented and discussed.
Heat Transfer From a Rotating Disc
Authors: Dibelius G. H. , Heinen M.
Published: March 2015

The local heat transfer from a plane rotating disc enclosed in a casing has been studied experimentally. The disc of 800 mm diameter can be run up to 2000 min−1 at axial distances between disc and casing varied between 5 and 55 mm. Centrifugal or alternatively centripetal flow of cooling air at rates up to ṁ = 1 kg/s can be applied, both with or without an inlet swirl.

With the disc rotating in a closed casing (ṁ = 0 kg/s) the influence of the characteristic dimensionless groups on the local heat transfer has been investigated. At a fixed radius, a variation of the local Reynolds Number by either speed or density results in corresponding changes of the heat transfer. However, with a variation of the radius different heat transfer-Re relations are found. In fact, the temperature distribution in the gas caused by the heat flux results in an additional influence of free convection, to be expressed by a Grashof Number. This is confirmed by a comparison of the experimental results with calculations based on Reynolds Analogy and measured friction coefficients. The discrepancies found can be explained only, if in addition to the limitations of the analogy, the influence of free convection is taken into account. Additional results of ongoing experiments concerning the influence of the geometry of the cavity between disc and casing, of the coolant flow rate and of the swirl are presented.
Numerical Prediction of Film Cooling Effectiveness and the Associated Aerodynamic Losses With a Three-Dimensional Calculation Procedure
Authors: Dibelius G. H. , Pitt R. , Wen B.
Published: March 2015

Film cooling of turbine blades by injecting air through holes or slots affects the main stream flow. A numerical model has been developed to predict the resulting three-dimensional flow and the temperature pattern under steady flow conditions. An elliptic procedure is used in the near injection area to include reverse flow situations, while in the upstream area as well as far downstream a partial-parabolic procedure is applied. As first step an adiabatic wall has been assumed as boundary condition, since for this case experimental data are readily available for comparison.

At elevated momentum blowing rates, zones of reverse flow occur downstream of the injection holes resulting in a decrease of cooling efficiency. A variation of the relevant parameters momentum blowing rate m, injection angle α and ratio of hole spacing to diameter s/d revealed the combination of m ≈ 1, α ≈ 30° and s/d ≈ 2 to be the optimum with respect to the averaged cooling efficiency and to the aerodynamic losses. Cooling is more efficient with slots than with a row of holes not considering the related problems of manufacture and service life. The calculated temperature patterns compare well with the experimental data available.
Energy Exchange and Secondary Losses Prediction in High Speed Axial and Radial Compressors
Authors: Kaldellis J. K. , Ktenidis P. D. , Kodossakis D. E.
Published: March 2015

In this paper an extension of our secondary flow calculation method is presented in order to estimate the energy exchange and the secondary losses in axial and radial compressors.

Although it is well known today that end-wall shear layers play a major role in the performance of the compressors, there are only few secondary flow methods able to predict realistically the behaviour of real machines. For this purpose a new theory was developed which extends Mellor’s basic principles and uses our previous work, including the complete form of meridional vorticity transport equation.

A coherent model for the real work exchange between the fluid and the machine has been developed, as well as for the distribution of secondary losses, not only at the compressor’s exit but also at every station through the machine. An expression for the added work due to the secondary field is also given. Finally the influence of secondary losses in the overall efficiency is well estimated.

This work has been successfully applied to a highly loaded compressor cascade, as well as to a transonic axial compressor and to a radial one-stage one. Comparison between theoretical and experimental results is also presented.
On the Design of Magnetic Suspension Systems
Authors: Sinha A.
Published: March 2015

First, the dynamic performance of magnetic suspension systems (Figures 1–3), which are designed on the basis of linear feedback laws, are examined. Then, nonlinear control laws are developed to make the dynamics of a suspension system to be exactly that of a linear spring-mass-damper system. It is found that such control laws are not defined for all initial conditions of the supported mass. Lastly, it is shown that it is possible to achieve a true spring-mass-damper behavior for all initial conditions by using two electromagnets, but operating only one at a time.
CT7-6: The Most Recent T700 Growth Derivative Engine
Authors: Kastrineli P. L. , Lightfoot W. E.
Published: March 2015

In June 1988, the most recent growth derivative of the successful T700 family of turboshaft/turboprop engines, the CT7–6, received its FAA type certificate. The CT7–6 is the latest model in the extensive T700/CT7 family of engines. Its design and certification program were the result of the growth derivative approach to meeting the customers’ demand for more power. This approach has been successfully used by GE Aircraft Engines to grow the T700/CT7 family to meet the needs of a wide variety of customers and aircraft applications around the world. T700/CT7 engines provide power to 14 different aircraft applications and have accumulated over 4.5 million hours of operation on nearly 6,000 engines.

This paper traces the evolution of the CT7–6 model and discusses the technology enhancements which were incorporated to make it the most powerful member of the T700/CT7 family. A description is given of the synergism in the design and test phase of the CT7–6, which resulted from the derivative approach in combination with an integrated development program that simultaneously qualified/certified four T700/CT7 engine models. The paper also reviews the initial operator experience with the CT7–6 in a unique new European aircraft, the EH Industries EH101 helicopter.
T407/GLC38: A Modern Technology Powerplant
Authors: Zoccoli Michael J. , Klassen David D.
Published: March 2015

The T407/GLC38 turboprop/turboshaft engine is a 6000 shaft horsepower (SHP) class gas turbine engine currently under joint development by Textron Lycoming of Stratford, Connecticut, and GE Aircraft Engines of Lynn, Massachusetts, with Bendix Control of South Bend, Indiana, a division of Allied Signal; Ruston Gas Turbines Limited of Great Britain, part of GEC ALSTHOM; and Steel Products Engineering Company (SPECO) of Springfield, Ohio.

The powerplant is derived from the highly successful GE27 Modern Technology Demonstrator Engine (MTDE) program, which was conducted under the auspices of the U.S. Army in the mid-1980s.

The T407 turboprop is currently under development for the U.S. Navy’s new P-7A anti-submarine warfare (ASW) aircraft. The P-7A will replace the P-3 and is under contract to Lockheed Aeronautical Systems Company (LASC). A T407 turboshaft model is also in development.

The GLC38 commercial turboprop version, planned for both business and commuter aircraft, draws considerably on lessons learned through GE and Textron Lycoming’s extensive commercial experience, thereby ensuring the latest state of the art in maintainability, life, reliability, and ease of operation.

The T407/GLC38 engine development program, scheduled for completion in December 1991, is uniquely defined to meet the stringent requirements of both Federal Aviation Administration (FAA) regulations and Military Specification MIL-E-008593E. The engine’s primary identity will be commercial, however, as per agreement with the U.S. Navy.

The engine’s gas generator core is also part of a joint venture between the Garrett Engine Division of Allied Signal Corporation and GE. Garrett is responsible for developing the fan and power turbine for a new generation turbofan engine, the CFE738.

This paper describes the key features of the T407/GLC38 engine design, performance, and development program.
Derivative T406 Based Turbofans for Advanced Trainers
Authors: Riffel R. E. , McKain T. F.
Published: March 2015

A need exists to modernize undergraduate pilot training procedures and resources to better address the emergence of new fighter/attack bomber and transport aircraft such as the ATF, A-12, B-1, B-2, C-17 and ATT. The current U.S. training resources consist of the T-37/T-38 aircraft for the Air Force and the T-45, which will replace the T-2C and the TA-4J, in the U.S. Navy pilot training program. The T-37 and T-38 aircraft are of the 1950s-1960s vintage and do not have the flying qualities, sustained G and Mach capability, and cockpit technologies consistent with now-emerging fighter/attack aircraft. The disparity in aircraft agility between today’s (and tomorrow’s) front line aircraft and trainers is illustrated in Fig. 1.
T406 Engine Development Program
Authors: Arvin John R. , Bowman Mark E.
Published: March 2015

The T406 engine development is discussed. The T406 is a 6000 horsepower class turboshaft, front drive, free turbine engine being developed under U.S. Navy contract to power the V-22 Osprey V/STOL aircraft. The V-22 is a subsonic airplane which uses tiltrotor technology to achieve V/STOL capabilities. The engine FSD program began in May of 1986 and will continue until May 1992.

A comprehensive engine description is given. The power/engine weight capability and growth potential make this engine the starting point for many future application.
Relationship Between Feedstock Characteristics and Erosivity of FBC Bed Materials
Authors: Levy Alan V. , Wang B. Q. , Geng G. Q.
Published: March 2015

The erosion-corrosion (E-C) metal wastage mechanisms and rates that occur in 1018 plain carbon steel used in tubular heat exchangers of fluid bed combustors (FBC) are discussed. The characteristics of FBC bed material erodent particles such as composition, shape, size and strength were found to have a major effect on the surface degradation mechanisms and rates which occurred. A total of sixteen different bed material particles from ten different FBCs were tested. It was determined that when the particles were strong enough to not shatter when they impacted the steel’s surface, their shape and composition were the most important factors in determining their erosivity.

The relative amounts of SiO2, CaO, CaCO3, CaSO4, and alkali compounds in the bed materials were related to the metal wastage by using laboratory mixtures of the compounds as erodents. The ratio of SiO2 to CaO and CaCO3 was especially important in determining the erosivity of the bed materials. It was found that increasing this ratio increased the metal wastage. A sharp transition ratio occurred on either side of which the metal wastages were linear. The slope of the linear curve was low for the lower sand content mixtures and higher for higher sand content mixtures. The transition ratio required a higher CaO content for higher velocity particles.
Optimizing Aircraft Performance With Adaptive, Integrated Flight/Propulsion Control
Authors: Smith R. H. , Chisholm J. D. , Stewart J. F.
Published: March 2015

An adaptive, integrated flight/propulsion control algorithm called Performance Seeking Control (PSC) has been developed to optimize total aircraft performance during steady state engine operation. The multi-mode algorithm will minimize fuel consumption at cruise conditions; maximize excess thrust (thrust minus drag) during aircraft accelerations, climbs, and dashes; and extend engine life by reducing Fan Turbine Inlet Temperature (FTIT) when the extended life mode is engaged. On-board models of the inlet, engine, and nozzle are optimized to compute a set of control trims, which are then applied as increments to the nominal engine and inlet control schedules. The on-board engine model is continually updated to match the operating characteristics of the actual engine cycle through the use of a Kalman filter, which accounts for anomalous engine operation. The PSC algorithm will be flight demonstrated on an F-15 test aircraft under the direction of the NASA Ames/Dryden Flight Research Facility. This paper discusses the PSC design strategy, describes the control algorithm, and presents results from high fidelity, nonlinear aircraft/engine simulations. Simulation results indicate that thrust increases as high as 15% and specific fuel consumption reductions up to 3% are realizable by the PSC system.
Heat Transfer Characteristics of Turbulent Flow in a Square Channel With Angled Discrete Ribs
Authors: Lau S. C. , McMillin R. D. , Han J. C.
Published: March 2015

Experiments have been conducted to study the turbulent heat transfer and friction for fully developed flow of air in a square channel in which two opposite walls are roughened with 90° full ribs, parallel and crossed full ribs with angles-of-attack (α) of 60° and 45°, 90° discrete ribs, and parallel and crossed discrete ribs with = 60°, 45°, and 30°. The discrete ribs are staggered in alternate rows of three and two ribs. Results are obtained for a rib height-to-channel hydraulic diameter ratio of 0.0625, a rib pitch-to-height ratio of 10, and Reynolds numbers between 10,000 and 80,000. Parallel angled discrete ribs are superior to 90° discrete ribs and parallel angled full ribs, and are recommended for internal cooling passages in gas turbine airfoils. For α = 60° and 45°, parallel discrete ribs have higher ribbed wall heat transfer, lower smooth wall heat transfer, and lower channel pressure drop than parallel full ribs. Parallel 60° discrete ribs have the highest ribbed wall heat transfer and parallel 30° discrete ribs cause the lowest pressure drop. The heat transfer and pressure drops in crossed angled full and discrete rib cases are all lower than those in the corresponding 90° and parallel angled rib cases. Crossed arrays of angled ribs have poor thermal performance and are not recommended.
Experimental Performance of a Heat Flux Microsensor
Authors: Hager J. M. , Simmons S. , Smith D. , Onishi S. , Langley L. W. , Diller T. E.
Published: March 2015

The performance characteristics of a heat flux microsensor have been measured and analyzed. This is a new heat flux gage system that is made using microfabrication techniques. The gages are small, have high frequency response, can measure very high heat flux, and output a voltage directly proportional to the heat flux. Each gage consists of a thin thermal resistance layer sandwiched between many thermocouple pairs forming a differential thermopile. Because the gage is made directly on the measurement surface and the total thickness is less than 2µm, the presence of the gage contributes negligible flow and thermal disruption. The active surface area of the gage is 3 mm by 4 mm, with the leads attached outside this area to relay the surface heat flux and temperature signals.

Gages were made and tested on glass and silicon substrates. The steady and unsteady response was measured experimentally and compared with analytical predictions. The analysis was performed using a one-dimensional, transient, finite-difference model of the six layers comprising the gage plus the substrate. Steady-state calibrations were done on a convection heat transfer apparatus and the transient response was measured to step changes of the imposed radiative flux. As an example of the potential capabilities, the time-resolved heat flux was measured at a stagnation point with imposed freestream turbulence. A hot-film probe placed outside the boundary layer was used to provide a simultaneous signal showing the corresponding turbulent velocity fluctuations.
Prediction of Cascade Performance Using an Incompressible Navier-Stokes Technique
Authors: Hobson G. V. , Lakshminarayana B.
Published: March 2015

A fully elliptic, control volume solution of the two-dimensional incompressible Navier-Stokes equations for the prediction of cascade performance over a wide incidence range is presented in this paper. The numerical technique is based on a new pressure substitution method. A Poisson equation is derived from the pressure weighted substitution of the full momentum equations into the continuity equation. The analysis of a double circular arc compressor cascade is presented, and the results are compared with the available experimental data at various incidence angles. Good agreement is obtained for the blade pressure distribution, boundary layer and wake profiles, skin friction coefficient, losses and outlet angles. Turbulence effects are simulated by the Low-Reynolds-Number version of the k-ε turbulence model.
Detailed Boundary Layer Measurements on a Transonic Turbine Cascade
Authors: Mee D. J. , Baines N. C. , Oldfield M. L. G.
Published: March 2015

The boundary layers of a transonic turbine blade have been measured in detail. The full velocity profiles have been measured at a number of stations on both the suction and pressure surfaces, at conditions representative of engine operation, using a pitot traverse technique and a large scale (300 mm chord) linear cascade. This information has made it possible to follow the development of the boundary layers, initially laminar, through a region of natural transition to a fully developed turbulent layer. Comparisons with other, less detailed, measurements on the same profile using pitot traverse and surface mounted thin films confirm the essential features of the boundary layers.
Status of the Industrial Applications of the Active Magnetic Bearings Technology
Authors: Dussaux Michel
Published: March 2015

This paper recalls the principle, technology, basic data and typical advantages of the active magnetic bearing.

Then it focuses on the main industrial applications of the active magnetic bearings and the status of these applications by the end of 1989.
Considerations for the Use of Variable Geometry in Gas Turbines
Authors: Roy-Aikins J. E. A.
Published: March 2015

The loss of performance of a gas turbine at off-design is primarily due to the rapid drop of the major cycle performance variables with decrease in output, and this may be aggravated by poor component performance. Postulated propulsion demands require that future engines attain performances much more advanced than those of the present day. The specific nature of the improvement in performance will depend on engine duty, but it is expected that the improvement will include higher power loadings and better response, in addition to better fuel burn characteristics.

Innovative design and advanced materials and structures will play key roles in bringing about a revolution in gas turbine technology, but these will have to be accompanied by novel control methods which can influence the position of the engine operating point. The latter may require the use of variable geometry in one or more gas path components to improve the internal matching of a component or to re-match the engine cycle such that the component operating point and/or the primary cycle performance variables are re-optimized or controlled with changing operating conditions. This paper examines how variable geometry could be used to improve the off-design performance of gas turbines.
Air Blast Atomization as a Function of Pressure Loss for Large Air Flow Rates
Authors: Hussain U. S. Abdul , Andrews G. E.
Published: March 2015

Combined air blast atomization and fuel and air mixing was studied in an interacting shear layer jet mixing flame stabilizer, termed Jet Mix, at gas turbine primary zone design conditions. Air blast atomization improves if large proportions of the combustion air flow are used and the maximum possible airflows were used in this study, as all the primary zone air flow was used for atomization. A Malvern spray analyser was used with a simulated gas-oil fuel. The atomization was investigated at 37 and 76 mm from the sprayer and there was a significant improvement in the atomization at the furthest downstream position. At gas turbine primary zone air flow pressure loss conditions, values of SMD below 20 microns were demonstrated and the results were lower than any other published air blast atomizer SMD for the same pressure loss. The results were correlated in terms of the atomizer air flow pressure loss and the pressure loss exponent varied from 0.9 to 0.6 as the blockage was increased. A general correlation for three different blockages was achieved with the constants a function of the blockage.
Effects of Gas Turbine Combustor Geometry Variation on Pollutant Emission Using a Multi-Annular, Telescopic, Swirl Combustor
Authors: Motevalli Vahid
Published: March 2015

A variable geometry swirl combustor, consisting of four concentric annuli was used to examine the effect of combustor geometry variation on pollutant emission. All annuli, except the central one, were equipped with vane-type swirl generators. Natural gas was used as the fuel. Air and fuel were introduced alternatively into the combustor annuli with the central annul us carrying the fuel. Species concentration measurements using gas chromatography, temperature measurements and NOx gas analysis were conducted to evaluate the combustor performance. Detailed species and temperature measurements were obtained over a radial distance of 1.5 times the combustor exit radius and up to 2.5 diameters down-stream of the combustor. A total swirl number for the combustor was determined from a theoretical formulation. It is shown here that finer control of the local equivalence ratio and air/fuel mixing may be achieved, yielding optimal combustion efficiencies and low pollutant emission, via variation of the combustor geometry.
Procedures for Shape Optimization of Gas Turbine Disks
Authors: Cheu Tsu-Chien
Published: March 2015

Two procedures, the feasible direction method and sequential linear programming, for shape optimization of gas turbine disks are presented in this paper. The objective of these procedures is to obtain optimal designs of turbine disks with geometric and stress constraints. The coordinates of the selected points on the disk contours are used as the design variables. Structural weight, stress and their derivatives with respect to the design variables are calculated by an efficient finite element method for design sensitivity analysis. Numerical examples of the optimal designs of a disk subjected to thermo-mechanical loadings are presented to illustrate and compare the effectiveness of these two procedures.
Full Coverage Impingement Heat Transfer at High Temperatures
Authors: Abdul Husain R. A. A. , Andrews G. E.
Published: March 2015

Transient cooling techniques were developed for the direct simultaneous measurement of full coverage multi-jet impingement heat transfer coefficient and cooling effectiveness under high temperature combustion convective wall heating conditions. A step change in the impingement coolant flow rate was made and the change in temperature recorded as a function of time, from which the heat transfer coefficient was calculated. A comparison between steady state and transient techniques was also made on a conventional low temperature electrically heated test facility and good agreement was found. There was reasonable agreement between the high temperature heat transfer coefficients and the low temperature results, using similar transient cooling techniques. There was little influence of the coolant to wall temperature ratio on the impingement heat transfer coefficient or the cooling effectiveness obtained from the high temperature test rig. The transient technique was used to study the influence of crossflow in the impingement gap on both the cooling effectiveness and the heat transfer coefficient for a range of low pressure loss impingement walls with an X/D of 1.9–11.