bluuebunny/crossref_metadata_2025 huggingface dataset:
Mixing in Axial Flow Compressors: Part II — Measurements in a Single Stage Compressor and a Duct
Authors: Li Y. S. , Cumpsty N. A.
Published: March 2015

This paper follows directly from Part I which contains not only the description of the facilities and the results for the C106 four-stage compressor but also the background, list of nomenclature, acknowledgement and references. The discussion and conclusions for Part I and Part II are given here. The single stage compressor results show the significant effects of inlet guide vane (IGV) wakes on mixing across the stage in the so called ‘free stream’ region; in the casing region tip clearance flow is shown to play an important role in mixing. Explanations for these results are given. Investigations were also carried out in a two-dimensional rectangular duct flow to reveal the mixing mechanism in the corner region similar to those formed by blade surfaces and endwalls in a compressor. Turbulent diffusion has been found to be the dominant mechanism in spanwise mixing; anisotropic inhomogeneous turbulent diffusion is mainly responsible for the non-uniform mixing in the corner region. The larger spread of tracer gas in the tangential direction than in the radial direction is mainly caused by the wake dispersion and relative flow motions within the blade wakes as well as secondary flow contributions in the end-wall regions.
Effects of Vortices With Different Circulations on Heat Transfer and Injectant Downstream of a Single Film-Cooling Hole in a Turbulent Boundary Layer
Authors: Ligrani P. M. , Subramanian C. S. , Craig D. W. , Kaisuwan P.
Published: March 2015

Results are presented which illustrate the effects of single embedded longitudinal vortices on heat transfer and injectant downstream of a single film-cooling hole in a turbulent boundary layer. Attention is focussed on the changes resulting as circulation magnitudes of the vortices are varied from 0.0 to 0.15 m**2/s. Mean temperature results are presented which show how injectant is distorted and redistributed by vortices, along with heat transfer measurements and mean velocity surveys. Injection hole diameter is 0.952 cm to give a ratio of vortex core diameter to hole diameter of about 1.5–1.6. The freestream velocity is maintained at 10 m/s, and the blowing ratio is approximately 0.5. The film-cooling hole is oriented 30 degrees with respect to the test surface. Stanton numbers are measured on a constant heat flux surface with a non-dimensional temperature parameter of about 1.5. Two different situations are studied: one where the injection hole is beneath the vortex downwash, and one where the injection hole is beneath the vortex upwash. For both cases, vortex centers pass well within 2.9 vortex core diameters of the centerline of the injection hole.

To quantify the influences of the vortices on the injectant and local heat transfer, the parameter S is used, defined as the ratio of vortex circulation to injection hole diameter times mean injection velocity. When S is greater than 1.0–1.5, injectant is swept into the vortex upwash and above the vortex core by secondary flows, and Stanton number data show evidence of injectant beneath the vortex core and downwash near the wall for x/d only up to 33.6. For larger x/d, local Stanton numbers are augmented by the vortices by as much as 23 percent relative to film-cooled boundary layers with no vortices. When S is less than 1.0–1.5, some injectant remains near the wall beneath the vortex core and downwash where it continues to provide some thermal protection. In some cases, the protection provided by film cooling is augmented because of vortex secondary flows which cause extra injectant to accumulate near vortex upwash regions.
Fabrication and Development of Axial Silicon Nitride Gas Turbine Rotors
Authors: Bandyopadhyay G. , French K. W. , Sordelet D. J. , Moergenthaler K. D.
Published: March 2015

Since 1984, GTE Laboratories Incorporated has performed research to develop net shape fabrication technology for axial silicon nitride rotors for the Daimler-Benz research gas turbine engine. The initial effort was focused on the fabrication of injection-molded profile discs. Subsequently, efforts were shifted to develop injection molding and slip casting technology for the bladed gasifier rotors. This joint activity has demonstrated that the ceramics technology has improved significantly over the last five years, as is evidenced by major improvement in properties and performance of silicon nitride components. The evolution of the ceramics fabrication technology at GTE and the role of improved process and NDE methods on components fabricated in recent years are described in this paper.
Design of Ceramic Gas Turbine Components
Authors: Stürmer G. , Fundus M. , Schulz A. , Wittig S.
Published: March 2015

At the Institute for Thermal Turbomachinery, University of Karlsruhe (ITS), detailed theoretical and experimental studies concerning ceramic gas turbine components are performed. For the analysis of the reliability of ceramic components by finite element calculations the numerical code CERITS has been developed which follows a strategy similar to that suggested by Gyekenyesi. CERITS determines the failiure probability of ceramic components with reference to volumetric flaws. Different fracture criteria can be considered. CERITS is coupled to the finite element code ADINA which facilitates the prediction of the required temperature and stress distributions. The procedure is demonstrated utilizing gas turbine combustor components.
Heat Transfer Measurements and Calculations in Transitionally Rough Flow
Authors: Hosni M. H. , Coleman Hugh W. , Taylor Robert P.
Published: March 2015

Experimental data on a rough surface for both transitionally rough and fully rough turbulent flow regimes are presented for Stanton number distribution, skin friction coefficient distribution and turbulence intensity profiles. The rough surface is composed of 1.27 mm diameter hemispheres spaced in a staggered array four base diameters apart on an otherwise smooth wall. Special emphasis is placed on the characteristics of heat transfer in the transitionally rough flows. Stanton number data are reported for zero pressure gradient incompressible turbulent boundary layer air flow for nominal freestream velocities of 6, 12, 28, 43, 58 and 67 m/s, which give x-Reynolds numbers up to 10,000,000. These data are compared with previously published rough surface data, and the classification of a boundary layer flow into transitionally rough and fully rough regimes is explored. Moreover, a new heat transfer model for use in the previously published discrete element prediction approach is presented. Computations using the discrete element model are presented and compared with data obtained from two different rough surfaces. The discrete element predictions for both surfaces are found to be in substantial agreement with the data.
Three-Dimensional Flow in an Axial Turbine: Part 2 — Profile Attenuation
Authors: Joslyn David , Dring Robert
Published: March 2015

This paper presents an exhaustive experimental documentation of the three–dimensional nature of the flow in a one–and–one–half stage axial turbine. The intent was to examine the flow within, and downstream of, both the stator and rotor airfoil rows so as to delineate the dominant physical mechanisms. Part 1 of this paper presented the aerodynamic results. Part 2 presents documentation of the mixing, or attenuation, of a simulated spanwise inlet temperature profile as it passed through the turbine including: (1) the simulated combustor exit–turbine inlet temperature profile, (2) surface measurements on the airfoils and endwalls of the three airfoil rows, and (3) radial–circumferential distributions downstream of each airfoil. Although all three rows contributed to profile attenuation, the impact of the rotor was strongest.
Thermogasdynamic Effects of the Engine Turbines With the Contra-Rotating Rotors
Authors: Sotsenko Y. V.
Published: March 2015

There were carried out the experimental investigations of the gas dynamic features and the analysis of the thermodynamic characteristics of the advanced engine turbines, designed with allowance for effects of the contra-rotating rotors. The investigations were performed on 12 rectilinear cascades with the different fluid deflection and meridional opening. The comparison of the obtained characteristics and the analysis of the flow pattern show the cascades for contra-rotating rotors have specific features which are necessary to take account while its designing.
Application of an Inverse Design Procedure to Axial Compressor Blading
Authors: Zedan Mohamed , Sehra Arun
Published: March 2015

A blade-to-blade inverse design procedure is presented for use in a quasi-3-D design system for multistage axial flow compressors. The procedure is applicable to transonic rotor and stator airfoil sections along axisymmetric stream surfaces. It accounts for the streamtube thickness and radius variations, and can be used in the analysis, fully inverse, and mixed inverse modes. Steady state Euler equations are implemented and formulated in terms of density and local displacement normal to streamline as dependent variables. Three test cases are presented in this paper to illustrate the application of this inverse design technique for optimizing rotor and stator airfoils of highly loaded, high pressure ratio compressor stages. These test cases demonstrate the capability of this procedure to optimize airfoil geometry for minimizing shock and diffusion losses without compromising the airfoil structural integrity.
Gas Turbine Power Plant Possibilities With a Nuclear Heat Source: Closed and Open Cycles
Authors: McDonald Colin F.
Published: March 2015

With the capability of burning a variety of fossil fuels, giving high thermal efficiency, and operating with low emissions, the gas turbine is becoming a major prime-mover for a wide spectrum of applications. Almost three decades ago two experimental projects were undertaken in which gas turbines were actually operated with heat from nuclear reactors. In retrospect, these systems were ahead of their time in terms of technology readiness, and prospects of the practical coupling of a gas turbine with a nuclear heat source towards the realization of a high efficiency, pollutant free, dry-cooled power plant has remained a long-term goal, which has been periodically studied in the last twenty years. Technology advancements in both high temperature gas-cooled reactors, and gas turbines now make the concept of a nuclear gas turbine plant realizable. Two possible plant concepts are highlighted in this paper, (1) a direct cycle system involving the integration of a closed-cycle helium gas turbine with a modular high temperature gas cooled reactor (MHTGR), and (2) the utilization of a conventional and proven combined cycle gas turbine, again with the MHTGR, but now involving the use of secondary (helium) and tertiary (air) loops. The open cycle system is more equipment intensive and places demanding requirements on the very high temperature heat exchangers, but has the merit of being able to utilize a conventional combined cycle turbo-generator set. In this paper both power plant concepts are put into perspective in terms of categorizing the most suitable applications, highlighting their major features and characteristics, and identifying the technology requirements.

The author would like to dedicate this paper to the late Professor Karl Bammert who actively supported deployment of the closed-cycle gas turbine for several decades with a variety of heat sources including fossil, solar, and nuclear systems.
Viscous Flow Field Calculations in High-Loaded Centrifugal Compressor Diffusers
Authors: Teipel Ingolf , Wiedermann Alexander
Published: March 2015

The topic of this paper is the computation of transonic turbulent flow fields in high-loaded centrifugal compressor diffusers with a time-marching scheme. A thin-layer approximation is introduced into the time-dependent Navier-Stokes equations and the turbulent quantities are provided by a zero-equation eddy-viscosity model due to Baldwin and Lomax. For solving the governing equations an explicit-implicit MacCormack scheme is applied. The effect of the side wall boundary layer can be employed globally by variable stream sheet thickness.

The present code has been verified by comparison of calculated and measured data. Pressure and velocity fields as well as global results like diffuser efficiency have been considered. The code is very efficient at a CRAY-XMP vector computer. Hence, two-dimensional and quasi-three-dimensional turbulent flow fields can be obtained with a reasonable effort. However, one has to be very careful concerning the modelling of the effect of the side-wall boundary layer by variable stream sheet thickness.
Gas Turbine Rotor Blade Film Cooling With and Without Simulated NGV Shock Waves and Wakes
Authors: Rigby M. J. , Johnson A. B. , Oldfield M. L. G.
Published: March 2015

Detailed heat transfer measurements have been made around a film-cooled transonic gas turbine rotor blade in the Oxford Isentropic Light Piston Tunnel. Film cooling behaviour for four film cooling configurations has been analysed for a range of blowing rates both without and with simulated nozzle guide vane (NGV) shock wave and wake passing. The superposition model of film cooling has been employed in analysis of time-mean heat transfer data, while time resolved unsteady heat transfer measurements have been analysed to determine interaction between film-cooling and unsteady shock wave and wake passing. It is found that there is a significant change of film-cooling behaviour on the suction surface when simulated NGV unsteady effects are introduced.
The LCF Behavior of Several Solid Solution Strengthened Alloys Used in Gas Turbine Engines
Authors: Srivastava S. K. , Klarstrom D. L.
Published: March 2015

LCF tests were performed on production plate (16mm thick) materials of HAYNES® alloy No. 230, HASTELLOY® alloy X and INCONEL® alloy 617. The tests were conducted in air at 760, 871 and 982°C under the fully reversed strain controlled mode on materials in the annealed condition. The results showed that 230™ alloy possesses the best low cycle fatigue characteristics followed by alloy X and alloy 617 under all test conditions. The paper presents total strain range-life data, cyclic hardening/softening, and metallographic observations on selected failed samples. It is shown that oxidation plays a key role in fatigue-crack initiation in alloy 617.
An Ultra-Low NOx Combustion System for a 3.5 MW Industrial Gas Turbine
Authors: Wilkes Colin , Mongia Hukam C. , Santanam Chandran B.
Published: March 2015

This paper presents the results obtained from a 1/8 th scale rich-quench-lean (RQL) combustor designed for ultra-low NOx operation running at Allison 501-K engine simulated full and part load conditions. The goal of the test program was to demonstrate the capability of the combustor to limit oxides of nitrogen (NOx) emissions to less than 10 ppmv and provide simultaneous control of carbon monoxide (CO) emissions to below 50 ppmv, both corrected to 15% oxygen. The tests were conducted on a refractory-lined bench scale combustor developed originally to support the advanced coal fired gas turbine program which is sponsored in part by the Department of Energy (DoE) Morgantown Energy Technology Center (METC). Measurements were made of NOx and CO emissions from natural gas (NG) and distillate fuel number 2 (DF#2) with water injection at simulated full and part power operation over a range of rich, quench and lean zone temperatures. The results show that the NOx goals of the test program were met and that CO emissions could be further controlled to less than 10 ppmvd on both fuels. The thermodynamic constraints of the system, the airflow splits and water injection rate requirements are discussed together with the combustor general design parameters. Estimates are also made for the required steam injection rate to produce the same NOx and CO emission levels.
Ultra-Low NOx Rich-Lean Combustion
Authors: Rizk N. K. , Mongia H. C.
Published: March 2015

An investigation has been carried out of the influence of the geometry and operating parameters of the rich/quench/lean (RQL) combustion concept on the NOx emissions. The RQL combustor is a three stage, variable geometry system in which fuel is burned in a carefully controlled fuel rich and fuel lean environment. The data utilized in this investigation were obtained under a wide range of operation that simulates the maximum continuous power mode, and for fuels that represent the future distillate types. An expression based on residence time, reaction rates, and mixing rates in each of the combustion zones was derived to estimate the NOx concentration. It was used also to define the range of operation that gives acceptable NOx for future applications. A 3-D combustor flow analysis was conducted to investigate the impact of various system components on the flow field and the total NOx. It was found that for further reduction of NOx modifications to the fuel nozzle and the quench mixer may be required.
Recent Progress in Research Pertaining to Estimates of Gas-Side Heat Transfer in an Aircraft Gas Turbine
Authors: Graham Robert W.
Published: March 2015

A decade ago several important fundamental heat transfer phenomena were identified which were considered basic to the ability to predict heat transfer loads in aircraft gas turbines. The progress in addressing these fundamentals over the past ten years is assessed in this paper. Much research effort has been devoted to their study in university, industry and government laboratories and significant progress has been achieved. Advances in computer technology have enabled the modeling of complex three-D fluid flow in gas turbines so necessary for heat transfer calculations. Advances in instrumentation plus improved data acquisition have brought about more reliable data sets. While much has advanced in the ‘80’s, much challenging research remains to be done. Several of these areas are suggested in the paper.
Cogeneration Plant Machinery Design for Maintenance and Reliability
Authors: Zirkelback Charles E.
Published: March 2015

This paper describes the major machinery used in a 108 megawatt combined cycle Cogeneration Plant at the Union Carbide’s Seadrift petrochemical complex. Philosophy of design, erection, start-up, and the first year of operation is discussed. Specific machinery problems and their remedies are described.
Experimental and Computed Performance Characteristics of High Speed Silicon Nitride Hybrid Ball Bearings
Authors: Hosang George W.
Published: March 2015

Development testing of hybrid bearings with M.50 rings and HIP’ed silicon nitride balls in small high speed turbojet engines was carried out for several minutes at speeds up to 110,000 rpm. The main rotor system comprised an overhung radial compressor and turbine monorotor assembly with a pair of preloaded 101–size bearings. Estimated aerodynamic thrust of up to 750 N (170 lb) was added to the 200 N (45 lb) preload on the bearing adjacent to the compressor. Some testing was carried out with MIL–L–7808 air/oil mist and some with JP–10 fuel supplied in a similar fashion.

After each test phase the bearings were removed for examination and re–used or replaced. Four of the bearings were submitted to inspection with special equipment to measure operating contact angles, as evidenced by the visible ball tracks, and any wear present.

Contact angles and other operating characteristics estimated with the Jones, “SHABERTH,” and “ADORE” computer codes were compared with the experimental data.
EJ200: The Engine for the New European Fighter Aircraft
Authors: Lane R. J. , Behenna J.
Published: March 2015

This paper describes the concept and design of the EJ200 engine to meet the air staff targets for the European Fighter Aircraft.

The international collaborative arrangements to support the programme are shown and the lessons learnt from previous collaboration illustrated.

The excellent progress made in the programme during the first year since the signing of the development contract is described to illustrate confidence in the ability to meet the design targets within the programme timescales.
Dynamic Control of Centrifugal Compressor Surge Using Tailored Structures
Authors: Gysling D. L. , Dugundji J. , Greitzer E. M. , Epstein A. H.
Published: March 2015

A new method for dynamic control of centrifugal compressor surge is presented. The approach taken is to suppress surge by modifying the compression system dynamic behavior using structural feedback. More specifically, one wall of a downstream volume, or plenum, is constructed so to move in response to small perturbations in pressure. This structural motion provides a means for absorbing the unsteady energy perturbations produced by the compressor, thus extending the stable operating range of the compression system.

In the paper, a lumped parameter analysis is carried out to define the coupled aerodynamic and structural system behavior and the potential for stabilization. First-of-a-kind experiments are then carried out to examine the conclusions of the analysis. As predicted by the model and demonstrated with experiment, a moveable plenum wall lowered the mass flow at which surge occurred in a centrifugal compression system by roughly 25% for a large range of operating conditions. In addition, because the tailored dynamics of the structure acts to suppress instabilities in their initial stages, this control was achieved with relatively little power being dissipated by the moveable wall system, and with no noticeable decrease in steady state performance. Although designed on the basis of linear system considerations, the structural control is shown to be capable of suppressing existing large amplitude limit cycle surge oscillations.
Wake Measurements and Loss Evaluation in a Controlled Diffusion Compressor Cascade
Authors: Shreeve R. P. , Elazar Y. , Dreon J. W. , Baydar A.
Published: March 2015

The results of two component laser-Doppler velocimeter (LDV) surveys made in the near wake (to one fifth chord) of a controlled diffusion (CD) compressor blade in a large scale cascade wind tunnel, are reported. The measurements were made at three positive incidence angles from near-design to angles thought to approach stall. Comparisons were made with calibrated pressure probe and hot-wire wake measurements and good agreement was found. The flow was found to be fully attached at the trailing edge at all incidence angles and the wake profiles were found to be highly skewed. Despite the precision obtained in the wake velocity profiles, the blade loss could not be evaluated accurately without measurements of the pressure field. The blade trailing edge surface pressures and velocity profiles were found to be consistent with downstream pressure probe measurements of loss, allowing conclusions to be drawn concerning the design of the trailing edge.
Unsteady Radial Transport in a Transonic Compressor Stage
Authors: Kotidis P. A. , Epstein A. H.
Published: March 2015

Time-resolved radial transport has been measured in a transonic compressor rotor by injecting a thin sheet of tracer gas upstream of the rotor and then surveying the tracer concentration at the rotor exit. The simultaneous, co-located, high frequency response measurements of local tracer gas concentration, total temperature, and total pressure made downstream of the rotor showed that most of the fluid transported radially appears in the blade wakes and that this fluid has considerably higher entropy than the circumferential mean. Both inward and outward fluid transport along the span was observed (3.5% of the total throughflow moved toward the tip while 1.6% moved toward the hub). Tracer concentration and fluid total temperature and pressure varied considerably from wake to wake, even on multiple samplings of the same blade. The time mean spreading rate inferred from these measurements is in general agreement with previously reported studies on multi-stage low speed compressors and is well predicted by the method of Gallimore and Cumpsty. It is suggested that a vortex street in the blade wakes could be responsible for both the observed radial transport and the large wake to wake variability. A quasi-three-dimensional model of a vortex street wake was developed and shown to be consistent with the data. The model predicts all of the inward transport but only 20% of the outward transport. It is hypothesized that outflow in separated regions on the blade suction surface is responsible for the remainder of the transport toward the rotor tip. Since the entropy, as well as the mass of the fluid transported radially, was measured, an estimate of the redistribution of loss in rotor due to radial fluid transport could be made. This showed that the effect of radial transport in this rotor was to move substantial loss from the rotor hub to tip, implying that a conventionally measured spanwise efficiency survey may not accurately represent the performance of individual blade sections.
Computation of Heat Transfer in Rotating Cavities Using a Two-Equation Model of Turbulence
Authors: Morse A. P. , Ong C. L.
Published: March 2015

The paper presents finite-difference predictions for the convective heat transfer in symmetrically-heated rotating cavities subjected to a radial outflow of cooling air. An elliptic calculation procedure has been used, with the turbulent fluxes estimated by means of a low Reynolds number k-ε model and the familiar ‘turbulence Prandtl number’ concept. The predictions extend to rotational Reynolds numbers of 3.7 × 106 and encompass cases where the disc temperatures may be increasing, constant or decreasing in the radial direction.

It is found that the turbulence model leads to predictions of the local and average Nusselt numbers for both discs which are generally within ± 10% of the values from published experimental data, although there appear to be larger systematic errors for the upstream disc than for the downstream disc. It is concluded that the calculations are of sufficient accuracy for engineering design purposes, but that improvements could be brought about by further optimization of the turbulence model.
More on the Turbulent-Strip Theory for Wake-Induced Transition
Authors: Mayle R. E. , Dullenkopf K.
Published: March 2015

A theory for transition from laminar to turbulent flow with an unsteady, periodic passing of turbulent wakes in the free stream has recently been presented by the authors. The theory considers a time-averaged transitional flow caused by the formation and propagation of turbulent strips along the surface. To apply the theory, however, both the origin and a quantity related to the production rate of these turbulent strips must be known. In this paper, after a brief review of the theory, a dimensional analysis of the problem is presented and data from experiments re-examined in light of the result. From this, an expression for the time-averaged intermittency is obtained which may be used to calculate the time-averaged distributions of various boundary layer quantities for wake-induced transitional flow.
Cooling-Air Injection Into Secondary Flow and Loss Fields Within a Linear Turbine Cascade
Authors: Yamamoto A. , Kondo Y. , Murao R.
Published: March 2015

In order to understand overall performance and internal flows of air-cooled turbine blade rows, flows in a model linear cascade were surveyed with secondary air injection from various locations of the blade surfaces. The secondary air interacted with the cascade passage vortices and changed the loss distribution significantly. The cascade overall loss decreased when the air was injected along the mainstream and increased when the air was injected against the mainstream from some locations of the blade leading edge. Effects on overall kinetic energy of the secondary flows and on the cascade outlet flow angle were also discussed in this paper.
Design and Development of a Research Combustor for Lean Blowout Studies
Authors: Sturgess G. J. , Sloan D. G. , Lesmerises A. L. , Heneghan S. P. , Ballal D. R.
Published: March 2015

In a modern annular aircraft gas turbine combustor, the phenomenon of lean blow out (LBO) is of major concern. To understand the physical processes involved in LBO, a research combustor was designed and developed to specifically reproduce recirculation patterns and LBO processes that occur in a real gas turbine combustor.

A total of eight leading design criteria were established for the research combustor. This paper discusses the combustor design constraints, aerothermochemical design, choice of combustor configurations, combustor sizing, mechanical design, combustor light-off, and combustor acoustic considerations that went into the final design and fabrication. Tests on this combustor reveal a complex sequence of events such as flame lift-off, intermittency, and onset of axial flame instability leading to lean blowout. The combustor operates satisfactorily and is yielding benchmark quality data for validating and refining computer models for predicting LBO in real engine combustors.
Jet Shear Layer Turbulent Diffusion Flames for Ultra-Low NOx Emissions
Authors: Al-Shaikhly A. F. Ali , Andrews G. E. , Aniagolu C. O.
Published: March 2015

Direct fuelling of each shear layer generated by an array of holes in a grid plate was shown to have ultra-low NOx emissions combined with a good flame stability, compared with a premixed system. Two methods of fuel injection were investigated that had opposite NOx/stability characteristics. Four shear layers in a 76 mm combustor were used at gas turbine primary zone operating conditions with 60% simulated primary zone air at one bar pressure. The fuels used were propane and natural gas and a minimum NOx emission of 2.5 ppm at 15% oxygen, compatible with a 0.1% inefficiency, was demonstrated for natural gas with a reasonable stability margin. These designs have the potential for a dry NOx solution to any current or proposed gas turbine NOx regulation for natural gas.
Assessment of Unsteady Flows in Turbines
Authors: Sharma O. P. , Pickett G. F. , Ni R. H.
Published: March 2015

The impact of unsteady flows research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations which identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.
Compressor Drum Aerodynamic Experiments and Analysis With Coolant Injected at Selected Locations
Authors: Johnson B. V. , Daniels W. A. , Kawecki E. J. , Martin R. J.
Published: March 2015

Experiments were conducted to determine the pressure distributions within a multi–cavity compressor drum model for two coolant injection locations and a range of flow conditions. Flow was injected through the upstream conical wall or through the cylindrical wall of the rotating model. The coolant flow, the drum rotational rate, and the model pressure were varied to produce a range of tangential and coolant flow Reynolds numbers, typical of large aircraft engine high pressure compressor drums. The experimental results were used to evaluate analytical procedures for predicting flow characteristics in rotating annular cavities with radially inward flow and for correlating flow characteristics in multiple–rotating annular cavities which are not currently predicted. Swirling flows, radially inward between compressor disks and within rotating annular cavities with no net flow, were analyzed with a procedure which coupled a viscous solution for the rotating core flow with a momentum integral analysis for the boundary layers on the disks. Constant viscosity and variable turbulent viscosity models were used in the analysis. Results from the analysis and the experiments were used to estimate the tangential velocity distribution in trapped cavities for two coolant injection configurations and a range of flow rates.
Prediction of Tip-Leakage Losses in Axial Turbines
Authors: Yaras M. I. , Sjolander S. A.
Published: March 2015

Existing methods for predicting the tip-leakage losses in turbomachinery are based on a variety assumptions, many of which have not been fully verified experimentally. Recently, several detailed experimental studies in turbine cascades have helped to clarify the physics of the flow and provide data on the evolution of the losses. The paper examines the assumptions underlying the prediction methods in the light of these data. An improved model for the losses is developed, using one of the existing models as the starting point.
Rotating Waves as a Stall Inception Indication in Axial Compressors
Authors: Garnier V. H. , Epstein A. H. , Greitzer E. M.
Published: March 2015

Stall inception has been studied in two low speed compressors (a single-stage and a three-stage) and in a high speed three-stage compressor, using temporally and spatially resolved measurements. In all three machines, rotating stall was preceded by a period in which small amplitude waves were observed travelling around the circumference of the machine at a speed slightly less than the fully developed rotating stall cell speed. The waves evolved smoothly into rotating stall without sharp changes in phase or amplitude, implying that, in the machines tested, the prestall waves and the fully developed rotating stall are two stages of the same phenomenon. The growth rate of these disturbances was in accord with that predicted by current analytical models. The prestall waves were observed both with uniform and with distorted inflow, but were most readily discerned with uniform inflow. Engineering uses and limitations of these waves are discussed.
Passive Control of Unstable Characteristics of a High Specific Speed Diagonal-Flow Fan by an Annular Wing
Authors: Kaneko Kenji , Setoguchi Toshiaki , Inoue Masahiro
Published: March 2015

A passive control of an unstable characteristics of a high specific speed diagonal-flow fan has been proposed. It is possible to eliminate the unstable characteristics of pressure-flow rate curve in a low flow region without deterioration of performance at design point. The control action is done naturally (passively) without any energy input. The inlet nozzle of an ordinary diagonal-flow fan was replaced by an annular wing with Göttingen 625 airfoil section. The mechanism of the passive control and the optimum geometrical parameter are discussed on the basis of the performance tests and internal flow measurements.
The F109-GA-100 Engine Designed Specifically for Trainer Use
Authors: Maertins Hans F. W. , Bruce Thomas W.
Published: March 2015

The F109-GA-100 (F109) engine, originally developed by Garrett under contract to the U.S. Air Force, is a state-of-the-art powerplant designed specifically for trainer use. The engine has been designed and demonstrated to be fully aerobatic capable, without limitations throughout the training envelope. To minimize student pilot workload, the engine features a full-authority digital electronic fuel control with automatic start and restart, automatic overspeed-/temperature-limiting, simple power management with no restrictions in operation and automatic thrust trim. Maintenance features include extensive built-in test and data logging to support effective life management. Designed for an 18,000-hour life to a duty cycle with a mission severity comparable to that of a fighter, the F109 has demonstrated exceptional durability and high reliability. This durability — coupled with excellent fuel efficiency that rivals a turboprop — resulted in extremely low life-cycle-cost (LCC) as demonstrated in accelerated mission testing.

This paper describes the design features of the F109 that establish this engine as a trendsetter for the 1990s and beyond.
The Particle-Wall, Normal-Impact Collision Coefficient in the Presence of a Liquid Film
Authors: Georgiou D. P. , Paleos G.
Published: March 2015

The turbine blades of Gas Turbines operating with “dirty” fuels are sometimes covered by a very thin liquid film, which originates from the condensation of the alkalic sulfates (mainly) in the flue gases. These films may influence drastically the collision coefficient of the impinging (ash) particles. This, in turn, influences the future trajectories of these particles and their adhesive properties, especially in the rotor blades where the Coriolis aceleration becomes a significant factor in the particle kinetic energy absorption process. The study reports on the capture film height and the variation of the collision coefficient with the film height. The experimental conditions correspond to those encountered in rotor blades, where the surface tension, the wave-making process and the boyancy all contribute to this energy absorption. The results indicate that the model based on the interaction of these factors gives a goodexplanation of the energy absorption process, except for the very thin height where particle apparent mass effects dominate the process.
A Simple and Reliable Combustion Control System
Authors: Becker B. , Bonsen F. , Simon G.
Published: March 2015

The basis of a simple and reliable control system is a low number of components to be controlled. In order not to bend the outer casing of the turbomachinery components during transients a symmetric arrangement of the combustors is required. Two combustors are then the lowest possible number. For modern dry-low-Nox burner systems with different modes of operation in the load range, more than one fuel nozzle system and the air flow distribution in the combustors have to be controlled. A low number of combustors therefore leads to a low number of such control devices.

The second key to a simple control systems is the design of the fuel nozzles. A return flow pressure atomizing system eliminates the need for more than one fuel nozzle per burner and for an atomizing air system. Gas nozzles not exhausting directly into the combustion zone eliminate the need for a gas nozzle purging system. To further improve the reliability of the system, the components are designed for maximum safety.
Combustor Exit Temperature Distortion Effects on Heat Transfer and Aerodynamics Within a Rotating Turbine Blade Passage
Authors: Harasgama S. P.
Published: March 2015

A numerical simulation of temperature distortion at inlet to a rotating turbine rotor has been performed. A 3D Navier-Stokes code the 2D boundary layer code - STAN5, have been used.

The results show that the hot gas is transported to the pressure surface of the blade and that hot gas also migrates to the blade pressure side tip. At locations greater than 50–60% axial chord the hot gas enters the tip-gap and emerges over the suction side. These computations are in agreement with previous experimental results.

The secondary flows within the turbine rotor are enhanced by the introduction of inlet radial temperature distortion and this is in accord with previous analytical work. It is shown that the heat flux near the tip region on the pressure side of the blade can be increased by up to 76% due to the re-distribution of the inlet temperature distortion.
Operating Experience in Refinery Application of the 13MW-Class Heavy Duty MF-111 Gas Turbine Engine
Authors: Masada J. , Fukue I.
Published: March 2015

A new, 13MW class, heavy duty gas turbine, the “MF-111” was developed for use as a prime mover for cogeneration, combined cycle and repowering applications. The use of such equipment in refineries presents special challenges as regards the combustion of nonstandard fuels, tolerance of industrial environments, and accomodation of site-specific design requirements. Such circumstances add substantially to the tasks of proving and adjusting the design of a new gas turbine, meeting stringent emissions requirements and introducing to the world of industrial gas turbines the benefits of F-class (1250°C burner outlet temperature) levels of thermodynamic performance.

This paper describes how these challenges have successfully been met during the three calendar years and ten machine-years of MF-111 refinery-application experience accumulated to-late.
Lubrication Oil Reservoir Mist Elimination
Authors: Belden Ronald D.
Published: March 2015

With emission standards becoming more and more stringent, reducing Lube Oil Reservoir Vent (LOV) mist emissions is receiving increased attention. This paper explores the nature of this oil mist, explains emission standards, describes some of the equipment that has been used in an attempt to control these emissions, and details the use of fiber beds in this application. Fiber beds have been more successful than other approaches at controlling LOV mist because of their ability to exceed emission standards with low pressure drop, minimal maintenance requirements, and guaranteed collection efficiency.
Development in Injection Molding Silicon Nitride Turbine Components
Authors: Neil J. , Bandyopadhyay G. , Sordelet D. , Mahoney M.
Published: March 2015

The use of injection molding technology for the fabrication of near-net-shape silicon nitride turbine components has been demonstrated in a number of rotor and blade configurations. The current emphasis at GTE Laboratories is to refine the process, bringing it to a level of durability and reproducibility sufficient for production needs. Progress in injection molding technology development will be described with emphasis on the flow and mechanical property requirements for forming flaw-free green components. Application of the findings to the fabrication of AGT-5 axial turbine rotors and vanes under the DOE sponsored Advanced Turbine Technology Applications Project will be reviewed.
An Analytical Approach to Reliability, Failure Forecasting and Product Quality
Authors: Byers James L.
Published: March 2015

Gas turbines and many other products can suffer from poor quality at different times in their life cycles. The cause may vary from mistakes in the manufacturing process to a design that does not meet the rigors of the actual usage environment. In many cases there is a huge negative impact on the cost of the warranty and hence on the bottom line of the producer as well as the user. The most logical place to start curing the problem lies not in an immediate redesign effort, but in quantifying the failure problem. This paper shows how a typical problem of failures impacting quality and the resulting warranty difficulty, can be solved by quantifying the future failure frequency, or failure forecasting. Once this is done it is possible to simply quantify the degree of improvement required and to control the costs in making the needed fixes. Since the failure forecasting solution can be done entirely on a desktop PC it is not a complicated or long drawn out process. Every engineer or analyst within the smallest to the largest company can make all of the required analyses in minutes for a simple problem and in an hour or so for many complex problems. Almost any conceivable product can be treated in this manner using the software available once the simple procedure is learned.
Probabilistic Analysis of Mistuned Bladed Disks: A Combined Closed Form-Perturbation Approach
Authors: Mignolet Marc P. , Christensen Karl R.
Published: March 2015

A two-step method is presented for the determination of reliable approximations of the probability density function of the forced response of a randomly mistuned bladed disk. Under the assumption of linearity, an integral representation of the probability density function of the blade amplitude is first derived. Then, deterministic perturbation techniques are employed to produce simple approximations of this function. The adequacy of the method is assessed by comparing several approximate solutions with simulation results.
A Small Gas Turbine for Drone Aircraft: Design Philosophy
Authors: Barbosa J. R. , Takeda A. S. , Monteiro J. F. C. , Mendonca M. T. , Ramsden K. W.
Published: March 2015

Low cost, and low weight, turbojet engines for RPV applications are being developed by the Aerospace Technical Centre in Brazil. A simple turbojet developing 320 N thrust is described which has been designed, manufactured and tested, succesfully matching its performance goals. Another turbojet developing 1000 N thrust has been designed and is currently being manufactured. This report describes the design philosophy adopted.
Centrifugal Compressor Impeller Aerodynamics: A Numerical Investigation
Authors: Dorney Daniel J. , Davis Roger L.
Published: March 2015

A three-dimensional, Navier-Stokes analysis is presented for the prediction of viscous flows through centrifugal impellers. Based on the Navier-Stokes rotor/stator interaction procedure developed by Rai, the present analysis uses a zonal grid methodology to discretize the impeller flow field and to facilitate the relative motion of the impeller. A blade surface oriented O-grid generated from an elliptic partial differential equation solution procedure is patched into an algebraically generated H-grid which is used to discretize the inlet, exit and blade-to-blade regions. The equations of motion are integrated using a spatially third-order accurate, implicit, iterative, upwind, finite difference, time-marching technique. Predicted results are presented for flow through a low speed centrifugal compressor impeller operating at design flow conditions. Comparison of these predicted results with experimental data demonstrates the capability of this procedure to predict impeller blade loading and provide insight into the secondary flow structure within the impeller blade passage.
Inlet Flow Distortion Effects on Rotating Stall
Authors: Fortin J. , Moffatt W. C.
Published: March 2015

For many years there has been a significant effort to better understand rotating stall/surge phenomena in axial compressors, as well as the effects of inlet flow distortions. Most experimental investigations to date, whether on laboratory compressors or on full scale jet engines, have tended to focus separately on the effects of these two flow disturbances on compressor performance. The purpose of the present study was to experimentally assess the influence of inlet flow distortions on the inception and nature of rotating stall in a full scale engine compressor. This paper reports results obtained for the first stage rotor of a 10-stage compressor subjected to screen-induced inlet pressure distortions. Previous investigations had shown that during part-speed operation, the front stages operated in rotating stall, and hot-film probe measurements made during the present study showed that the presence of the distortion screens did not affect the speed of the rotating stall pattern, but in some instances changed the number of cells present. However, low frequency flow fluctuations characteristic of surge were much more prevalent when the screens were in place. Also, the further the sensing probe was displaced tangentially in the rotor rotation direction from the screens, the more intense the fluctuations, leading one to conclude that the screens had a localized damping effect on the surge cycle.
Wake Mixing Improvements in a Linear Compressor Cascade With Crenulated Trailing Edges
Authors: Veesart J. L. , King P. I. , Elrod W. C. , Wennerstrom A. J.
Published: March 2015

Trailing edge crenulations offer one possible way of energizing the trailing edge wakes from a gas turbine engine compressor blade by creating small vortices as a result of the pressure differential between the suction surface and pressure surface. The effect of crenulated trailing edges on wake dissipation and mixed-out total pressure loss in a linear, subsonic, compressor cascade was investigated for three low aspect ratio blade configurations: one with no crenulations and two others with large and small crenulation patterns, respectively. The effect of crenulations was to improve the wake mixing and reduce the velocity deficit. larger crenulations dissipated the wake most rapidly, and both crenulation configurations offered an improvement in total pressure loss and some improvement in flow turning.