bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of Axial Compressor Fouling in High Ambient Temperature Conditions
Authors: Haq Inamul , Saravanamuttoo H. I. H.
Published: March 2015

This paper discusses gas turbine engine health monitoring with a fleet of 3 MW units operating at ambient temperatures up to 45 °C. The engines operate continuously near the topping temperature and cannot tolerate a significant performance loss due to compressor fouling. Various parameters indicating engine health condition were investigated and the single best parameter was found to be compressor delivery pressure. A simple predictive monitoring scheme was developed for assessing the degree of compressor fouling to help in optimizing the time between compressor washes.
Nickel Base Alloy GTD-222, a New Gas Turbine Nozzle Alloy
Authors: Seaver D. W. , Beltran A. M.
Published: March 2015

This paper summarizes the key properties of GTD-222 (1), a new cast nickel base nozzle alloy developed by GE for use in land based gas turbines. GTD-222 is being introduced as a replacement for FSX-414 in second and third stage nozzles of certain machines. Presented in this paper are comparisons of the tensile, creep-rupture, and fatigue properties of GTD-222 versus FSX-414. In addition, the results of a long term thermal stability study, high temperature oxidation and hot corrosion evaluation as well as weldability results will be discussed.
The Efficiencies of Single-Stage Centrifugal Compressors for Aircraft Applications
Authors: Rodgers C.
Published: March 2015

The thrust of most recent advances in single– and two–stage centrifugal compressor technology by the aerospace community has been motivated by interest in increasing airbreathing propulsion system power density, and improving specific fuel consumption with higher stage pressure ratios. Advances in the last decade have made it appropriate to review the major design parameters influencing the efficiency levels of single–stage centrifugal compressors for aircraft applications.

A simple efficiency correlation was derived for advanced single–stage centrifugal compressors. It was based upon four critical parameters:

• Inlet Specific Speed

• Impeller Tip Diameter

• Inducer Tip Relative Mach Number

• Exit Discharge Mach Number

The correlation was shown to predict attainable state–of–the–art efficiencies within a band width of ± 2 % points. This was considered acceptable for preliminary compressor and engine design work.
Theory of Finite Disturbances in a Centrifugal Compression System With a Vaneless Radial Diffuser
Authors: Moore F. K.
Published: March 2015

A previous small-perturbation analysis of circumferential waves in centrifugal compression systems, assuming inviscid flow, is first shown to be consistent with observations that narrow diffusers are more stable than wide ones, when boundary-layer displacement effect is included.

Then, a previous analysis for finite-strength transients containing both surge and rotating stall in axial machines is adapted for a centrifugal compression system. Under certain assumptions, and except for a new second-order swirl, the diffuser velocity field, including resonant singularities, can be carried over from the previous inviscid, linear analysis.

Nonlinear transient equations are derived and applied in a simple example to show that throttling through a resonant value of flow coefficient must occur in a sudden surge-like drop, accompanied by a transient rotating wave. This “inner” solution is superseded by an “outer” surge response on a longer time scale. Numerical results are shown for various parametric choices relating to throttle schedule and the characteristic slope.
Unsteady Viscous Flow in a High Speed Core Compressor
Authors: Cherrett M. A. , Bryce J. D.
Published: March 2015

A probe incorporating a miniature high-frequency response pressure transducer has been traversed behind the first three stages of a high-speed multistage compressor operating at throttle settings corresponding to near choke, peak efficiency and near surge. A novel method of compensating for transducer temperature sensitivity was employed. Consequently, time-averaged pressures derived from the transducer were found to be in good agreement with pneumatic pressure measurements. Analysis of the unsteady pressure measurements revealed both the periodic and random fluctuations in the flowfield. This provided information on rotor-rotor interaction effects and the nature of viscous blade wake and secondary flows in each stage.
Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage
Authors: Zeschky J. , Gallus H. E.
Published: March 2015

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data includes the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution.

The formation of the tip clearance vortex and the passage vortices is presented, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.
Rotating Stall Flow and Dangerous Blade Excitation of Centrifugal Compressor Impeller: Part 1 — Phenomenon of Large-Number Stall Cells
Authors: Seidel U. , Chen J. , Haupt U. , Hasemann H. , Jin D. , Rautenberg M.
Published: March 2015

A new structure of rotating stall with unusual large-number stall cells (up to 7) has been detected experimentally in a high performance single stage centrifugal compressor system with backswept impeller and vaned diffusers. The number of stall cells is firstly identified by a phase analysis of pressure signals obtained from fast response dynamic transducers located at different circumferential positions on the shroud wall, and then verified by comparing the resulting frequencies of blade vibration with that measured from blade mounted strain gages. Up to 6 transducers in one radial position have been used for more certainty of the phase analysis. For the case of intermittent stall patterns, the frequency analysis of pressure and blade vibration signals is performed separately for sections with different characters of oscillation to avoid the smearing effect if signals of the whole pattern are averaged. As a result, the large-number stall cells, numbered 4–7, were determined in the speed range of 12000–14000 rpm, and in the higher speeds of 15000–16000 rpm right after the occurrence of normal stall cells of 2, when the flow rate is slightly reduced along the constant speed line.

For the large-number stall cell case, the measured blade vibration strain has reached such a high level that is already beyond the tolerance of blade material. Moreover, frequencies of blade excitation are always in the vincinity of resonance. These two features, which are not observed for the normal stall cell case and for the excitation of broadband character, show a particular danger of this phenomenon to the compressor operation.
Characterization and Modeling of Tensile Behavior of Ceramic Woven Fabric Composites
Authors: Kuo Wen-Shyong , Chen Wennei Y. , Parvizi-Majidi Azar , Chou Tsu-Wei
Published: March 2015

This paper examines the tensile behavior of SiC/SiC fabric composites. In the characterization effort, the stress-strain relation and damage evolution are studied with a series of loading and unloading tensile test experiments. The stress-strain relation is linear in response to the initial loading and becomes nonlinear when loading exceeds the proportional limit. Transverse cracking has been observed to be a dominant damage mode governing the nonlinear deformation. The damage is initiated at the inter-tow pores where fiber yarns cross over each other. In the modeling work, the analysis is based upon a fiber bundle model, in which fiber undulation in the warp and fill directions and gaps among fiber yarns have been taken into account. Two limiting cases of fabric stacking arrangements are studied. Closed form solutions are obtained for the composite stiffness and Poisson’s ratio. Transverse cracking in the composite is discussed by applying a constant failure strain criterion.
Inner Operation of Prefilming Airblast Atomizers
Authors: Gan Xiaohua , Zhao Qishou
Published: March 2015

In this paper research is focused on the inner operation of prefilming airblast atomizers and its effect on liquid atomization. Liquid wavy film thickness and wavelength-frequency spectra, which characterize the liquid motion inside the atomizers, are measured with specifical techniques. The motion and separation of liquid wavy film are picturized by means of laser pulse micrography technique. The spray is measured with the Malvern Particle Sizer. The experiments show the liquid atomization is initiated by separation of the liquid film waves from their main film. The atomization characteristics are dominated by the extent of air/liquid interaction inside the atomizers. In addition, liquid flow rate effect on atomization is comfirmed. No liquid collection near the atomizer edges is found.
An Atomization Model and Computation of a Prefilming Airblast Atomizer
Authors: Gan Xiaohua , Zhao Qishou
Published: March 2015

In the present paper, anatomization model for a prefilming airblast atomizer is constructed and put into numerical computation. A separation criterion is suggested to judge the liquid wavy film disintegration. Quantitative relationships between the spray and the wavelength-frequency spectrum of the liquid wavy film are analysed. A computational method called Trace-Statistics is developed to trace the liquid wavy film separation and droplet motion. Through statistical computation of the droplets, desired parameters of spray distributed in the calculated plane can be obtained. A computation example of the model is demonstrated. Its results agree with the experiments.
The Parametric Study of Ignition Process of a Fuel Droplet
Authors: Char Jir-Ming , Fan Mao-Yi
Published: March 2015

Combustion of a single fuel droplet has long been studied because it establishes the background of understanding the behavior of spray combustion. Ignition is the most critical process during its life time. According to a practical ignition criterion, many parametric studies are performed to examine the effects on ignition under different droplet conditions and different ambient conditions. In addition, two liquid-phase models, infinite conductivity model and conduction limit model, are discussed to demonstrate the heating effect of droplet itself. Dual-period concept is introduced to clarify the dominant factor that governs the ignition process. A special hybrid numerical scheme, ICED-ALE, is used to resolve the difficulties arising from the rapid transition of ignition and regression behavior of a fuel droplet. The numerical predictions show good agreement with the experimental data.
Comparative Evaluation of Combustion Codes for Low-Btu Gas Applications
Authors: Yang Tah-Teh , Agrawal Ajay K.
Published: March 2015

Four computer codes (PHOENICS, PCGC, FLUENT and INTERN) representing a spectrum of existing combustion modeling capabilities were evaluated for low-Btu gas applications. In particular, the objective was to identify computer code(s) that can be used effectively for predictions of (a) the flow field to yield efficient combustion, (b) the temperature field to ensure structural integrity and (c) species concentrations to meet environmental emission standards in a gas turbine combustor operating on low-Btu coal gas. Detailed information on physical models, assumptions, limitations and operational features of various codes was obtained through a series of computational runs of increasing complexity and grouped as (a) experimental validation, (b) code comparison and (c) application to coal gas combustion.

INTERN is not suitable for the present application since it has been tailored to model combustion process of premixed hydrocarbon fuels. FLUENT is easy to use and has detailed combustion models (in Version 3), however, it is not favored here because the user is unable to alter, modify or change the existing model(s). While PCGC-2 has the most comprehensive models for combustion, it is not user friendly and is inherently limited to axisymmetric geometry. PCGC-3 is expected to overcome these drawbacks. Built in combustion models in PHOENICS are similar to those in FLUENT. However, the user can implement advanced models on PHOENICS leading to a flexible and powerful combustion code.
Effects of Simulated Rotation on Tip Leakage in a Planar Cascade of Turbine Blades: Part I — Tip Gap Flow
Authors: Yaras M. I. , Sjolander S. A.
Published: March 2015

The paper presents further results from a continuing study on tip leakage in axial turbines. Rotation has been simulated in a linear cascade test section by using a moving-belt tip wall. Measurements were made inside the tip gap with a three-hole pressure probe for a clearance size of 3.8 percent of the blade chord. Two wall speeds are considered and the results are compared with the case of no rotation. As in other experiments, significant reduction in the gap mass flow rate is observed due to the relative motion. The detailed nature of the measurements allows the dominant physical mechanism by which wall motion affects the tip gap flow to be identified. Based on the experimental observations, an earlier model for predicting the tip gap flow field is extended to the case of relative wall motion. Part II of the paper examines the effect of the relative motion on the downstream flow field and the blade loading.
Effects of Simulated Rotation on Tip Leakage in a Planar Cascade of Turbine Blades: Part II — Downstream Flow Field and Blade Loading
Authors: Yaras M. I. , Sjolander S. A. , Kind R. J.
Published: March 2015

This paper and its companion paper present experimental results on the effects of simulated rotation on the tip leakage in a linear turbine cascade test. Part II examines the downstream flow field. For clearance sizes of 2.4 and 3.8 percent of the blade chord measurements were made in two planes downstream of the trailing edge using a seven-hole pressure probe. Significant changes in the tip leakage vortex and passage vortex structures are observed with the introduction of relative motion. The effects of clearance size and rotation on the relationship between bound circulation and tip-vortex circulation are discussed. The validity of a previously developed tip-vortex model for the case of rotation is examined in the light of the measurements. Finally, for clearances of 1.5, 2.4 and 3.8 percent of the blade chord the effects of rotation on blade loading are studied through static pressure measurements on the blade surfaces. The distortion of the surface pressure field near the tip is found to be reduced with increasing wall speed. This is consistent with the reduced strength of the tip-leakage vortex as wall speed is increased. For all measurements two wall speeds are considered and the results are compared with the case of no rotation.
The Effect of Steady Aerodynamic Loading on the Flutter Stability of Turbomachinery Blading
Authors: Smith Todd E. , Kadambi Jaikrishnan R.
Published: March 2015

An aeroelastic analysis is presented which accounts for the effect of steady aerodynamic loading on the aeroelastic stability of a cascade of compressor blades. The aeroelastic model is a two degree-of-freedom model having bending and torsional displacements. A linearized unsteady potential flow theory is used to determine the unsteady aerodynamic response coefficients for the aeroelastic analysis. The steady aerodynamic loading was caused by the addition of (1) airfoil thickness and camber and (2) steady flow incidence. The importance of steady loading on the airfoil unsteady pressure distribution is demonstrated. Additionally, the effect of the steady loading on the tuned flutter behavior and flutter boundaries indicates that neglecting either airfoil thickness, camber or incidence could result in nonconservative estimates of flutter behavior.
Separating Hydrogen From Coal Gasification Gases With Alumina Membranes
Authors: Egan B. Z. , Fain D. E. , Roettger G. E. , White D. E.
Published: March 2015

Synthesis gas produced in coal gasification processes contains hydrogen, along with carbon monoxide, carbon dioxide, hydrogen sulfide, water, nitrogen, and other gases, depending on the particular gasification process. Development of membrane technology to separate the hydrogen from the raw gas at the high operating temperatures and pressures near exit gas conditions would improve the efficiency of the process.

Tubular porous alumina membranes with mean pore radii ranging from about 9 to 22 A have been fabricated and characterized. Based on the results of hydrostatic tests, the burst strength of the membranes ranged from 800 to 1600 psig, with a mean value of about 1300 psig. These membranes were evaluated for separating hydrogen and other gases.

Tests of membrane permeabilities were made with helium, nitrogen, and carbon dioxide. Measurements were made at room temperature in the pressure range of 15 to 589 psi. In general, the relative gas permeabilities correlated qualitatively with a Knudsen flow mechanism; however, other gas transport mechanisms such as surface adsorption may also be involved.

Efforts are under way to fabricate membranes having still smaller pores. At smaller pore sizes, higher separation factors are expected from molecular sieving effects.
Wind Tunnel Wall Effects in a Linear Oscillating Cascade
Authors: Buffum D. H. , Fleeter S.
Published: March 2015

Experiments in a linear oscillating cascade reveal that the wind tunnel walls enclosing the airfoils have, in some cases, a detrimental effect on the oscillating cascade aerodynamics. In a subsonic flow field, biconvex airfoils are driven simultaneously in harmonic, torsion-mode oscillations for a range of interblade phase angle values. It is found that the cascade dynamic periodicity — the airfoil-to-airfoil variation in unsteady surface pressure — is good for some values of interblade phase angle but poor for others. Correlation of the unsteady pressure data with oscillating flat plate cascade predictions is generally good for conditions where the periodicity is good and poor where the periodicity is poor. Calculations based upon linearized unsteady aerodynamic theory indicate that pressure waves reflected from the wind tunnel walls are responsible for the cases where there is poor periodicity and poor correlation with the predictions.
Advanced Ducted Engines Nacelle Aerodynamics and Integration Testing
Authors: McCall J. E. , Tracksdorf Peter , Heinig Klaus
Published: March 2015

Future aircraft engine development may lead to Advanced Ducted Engines (ADE) which have a bypass ratio significantly higher than present turbofans. The increases in bypass ratio will dictate larger diameter nacelles and an increasing importance of the nacelle aerodynamics and wing integration aerodynamics.

A series of isolated wind tunnel tests was therefore designed and conducted by PWA and MTU to investigate inlet, nozzle and reverser aerodynamics. Additional installed testing was done in cooperation with MBB and BAe. Key features of the tests are noted and significant results are discussed.
The Utilization of Computer Aided Drafting (CAD) in Quality Control of Gas Turbine Component Repairs
Authors: Baldwin Darla J.
Published: March 2015

In order to maintain a proper standard of excellence in any company a Quality Control program must be implemented. This program must be designed to ensure adequate quality is being provided to the customer. A thorough Inspection Department is of utmost importance in establishing a proper Quality Control system where every step of the repair process is monitored and recorded. All documentation produced should be of the highest quality standards possible which can be obtained through the use of Computer Aided Drafting (CAD). It is the intent of this paper to demonstrate how CAD can be utilized throughout the Quality Control process in order to provide clear, accurate and concise information for the customer as well as the company.
Mission Design Drivers for Closed Brayton Cycle Space Power Conversion Configuration
Authors: Baggenstoss William G. , Ashe Tom L.
Published: March 2015

Future space power requirements will vary from the subkilowatt range for deep space probes, to the hundreds of kilowatts range for a lunar base, to the multimegawatt range for interplanetary propulsion systems. Closed Brayton cycle (CBC) power conversion has the flexibility to be used in all these power ranges and with a variety of heat source options such as isotope, solar, and nuclear. Each of these types of heat sources has different characteristics that make it more appropriate for particular mission profiles and power output ranges. Heat source characteristics can also be major design drivers in the closed Brayton cycle design optimization process.

This paper explores heat source selection, the resulting CBC system designs, and discusses optimization methods as a function of the main design drivers. Such power system requirements as power level, man-rated radiation shielding, fuel costs, eclipse/darkness duration, system mass, radiator area, reliability/mission duration, and insolation level are evaluated through several CBC parametric case studies. These cases include:

(1) A 500 We power system for deep space probes,

(2) A 50 kWe solar dynamic system for earth orbit and other applications,

(3) A 100 kWe man-rated lunar/Mars stationary/rover power system,

(4) A 200 to 825 kWe power system for the lunar outpost, and

(5) 3300 kWe modules for interplanetary propulsion.
NASA Low-Speed Centrifugal Compressor for 3-D Viscous Code Assessment and Fundamental Flow Physics Research
Authors: Hathaway M. D. , Wood J. R. , Wasserbauer C. A.
Published: March 2015

A low speed centrifugal compressor facility recently built by the NASA Lewis Research Center is described. The purpose of this facility is to obtain detailed flow field measurements for computational fluid dynamic code assessment and flow physics modelling in support of Army and NASA efforts to advance small gas turbine engine technology. The facility is heavily instrumented with pressure and temperature probes, both in the stationary and rotating frames of reference, and has provisions for flow visualization and laser velocimetry. The facility will accommodate rotational speeds to 2400 rpm and is rated at pressures to 1.25 atm. The initial compressor stage being tested is geometrically and dynamically representative of modern high-performance centrifugal compressor stages with the exception of Mach number levels. Preliminary experimental investigations of inlet and exit flow uniformity and measurement repeatability are presented. These results demonstrate the high quality of the data which may be expected from this facility. The significance of synergism between computational fluid dynamic analyses and experimentation throughout the development of the low speed centrifugal compressor facility is demonstrated.
TMFSLAM-Design Analysis Tool for Coated Structures
Authors: Bechtel G. S. , McKnight R. L. , Cook T. S.
Published: March 2015

Hot flowpath components in aircraft gas turbine engines are subject to a severe operating environment. The large thermal gradients can produce high thermal strains which, when combined with mechanical loads and a deleterious environment, can lead to premature failure. To combat this possibility, designers spend considerable time determining the stress and strain fields in these components as the parts undergo typical operating histories. These field quantities can then be used to determine failure parameters and determine life limiting locations. The field determinations can be difficult and, in combination with numerous potential failure mechanisms, the structural assurance process can take a considerable time to complete. To shorten this process, a personal computer (PC) based preliminary design system has been developed. This system, called Thermomechanical Fatigue – Structural Life Assessment Method (TMFSLAM), permits the user to rapidly evaluate the interactive effects of duty cycle, geometry, and materials on component life. The quantitative results determined by TMFSLAM will be available to make decisions on design changes, material substitution, etc.
Multi-Blade Row Navier-Stokes Simulations of Fan-Bypass Configurations
Authors: Dawes W. N.
Published: March 2015

This paper describes extensions to a multi-blade row 3D Navier-Stokes solver to enable fan-splitter-bypass geometries to be handled. The code is applied to two generic configurations. The core-bypass splitter can exert considerable upstream influence via its associated pressure field and in the example shown here severely disturbs the fan suction surface boundary layer. The behaviour of the bypass ogv is substantially modified both by the clearance flow of the upstream fan and also by thicker than expected boundary layers on the splitter upper surface caused by the splitter LE incidence associated with the particular bypass ratio selected for the example.
Experiments on the Blade Loss Transient Response of Rotor With Flexible Damped Support
Authors: Li Qihan , Zhang Shiping , Yan Litang , Zhao Fuan
Published: March 2015

The purpose of this paper is to present some experimental results on the transient response dynamics of a rotor system with flexible damped support due to the event of simulated blade loss.

Experiments under different sudden unbalances applied on the rotor system with various SFD film clearances at different rotational speeds were performed. The instability conditions characterized by limiting circle orbits for large amplitude at damper location were determined and some special phenomena such as lock up, bistable jump and subharmonic etc. have been observed. The effectiveness and the capability of SFD for suppressing instability are analyzed.
Progressive Damage in Unidirectional Ceramic Composites Under Transient Thermal Fatigue
Authors: Sinha A. , Kokini K. , Bowman K. J.
Published: March 2015

The changes in stiffness properties for a CAS matrix-Nicalon fiber unidirectional composite resulting from cyclic heating and cooling are presented. The measurements are made using an ultrasonic pulse-echo technique. It is shown that a significant decrease in stiffness is observed after 30 cycles.
Development of Silicon Nitride Rotors for the ATTAP Program at Garrett Ceramic Components
Authors: Busovne B. J. , Pollinger J. P.
Published: March 2015

The development and fabrication of reliable high temperature-high strength silicon nitride rotors by Garrett Ceramic Components (GCC) for the Advanced Turbine Technology Applications Project (ATTAP) is discussed. GCC’s progress will be presented, including mechanical properties characterization, in-process monitoring development, and extensive NDE analysis. The current status of material, process, and part properties of the rotors being developed will be compared to properties required for implementation and successful operation of advanced gas turbine engines at 2500°F.
Unsteady Euler Calculations in 2-D Internal Aerodynamics With Introduced Vorticity
Authors: Hadzidakis M. , Karagiannis F. , Chaviaropoulos P. , Papailiou K. D.
Published: March 2015

This paper presents an implicit finite difference algorithm which solves the unsteady Euler equations in two-dimensional ducts. The unsteady nature of the flow is due to the time dependent inflow and outflow boundary conditions, while the geometry does not change in time. The present work is based on the Helmholtz decomposition of the unsteady velocity field into a potential and a rotational part. Vorticity is introduced at the inlet by means of velocity, total enthalpy or even entropy slope. The presented results cover a wide range of reduced frequencies in the subsonic regime.
A Calculation Model of the Secondary Flow Loss for Leaned Stator Cascade
Authors: Zhang Zhi-Gang , Zhou Dong-Mei , Li Yan-Sheng
Published: March 2015

An approach to the estimation of losses produced by the secondary flow near the hub and casing of turbine cascade with leaned blades is presented after discussing the generation of secondary flow and the effect of some important factors on losses. The loss system is a development of the method in [9] and [10], but results obtained by comparing with experimental data are encouraging.
The Influence of Shock Waves on the Viscous Flow Field of Axial Compressors
Authors: Kaldellis J. K. , Katramatos D. T. , Ktenidis P. D.
Published: March 2015

Changes in flow field due to the presence of shock waves in axial compressors are examined in the present work. A simple but realistic model is used to predict the static pressure, the relative Mach number, the total pressure and the total temperature distributions through the shock region. These distributions are strongly affected by the interaction between the shock waves and the shear layers or the secondary flow field.

Our well documented secondary flow code along with our fast compressible shear layer calculation method are utilized in order to provide the necessary quantities of the viscous flow for the approximate shock-viscous flow interaction procedure. The shock induced losses, along with the increased shear layer or secondary flow losses, are also predicted.

The complete procedure is successfully applied to several test cases including separation. The results of the proposed method are compared with results of previous calculations and the available experimental data.

Finally, the flow field through the rotor of a supersonic compressor is thoroughly analyzed, and major conclusions concerning the modification of the secondary flow field due to the shock wave appearance are given.
Development of a Repair for the Annulus in a Radial Turbine Wheel
Authors: Rose Daniel P. , Price George , Milidantri Thomas
Published: March 2015

The Garrett GTCP85 engine is used to provide electrical power and compressed air for commercial aircraft, including the Boeing 727 and 737, and the McDonnell Douglas DC-9 and MD-80. The turbine section of this engine consists of a radial flow turbine rotor and stationary nozzle shroud. The turbine rotor configuration on some of the engine models is a two-piece separable assembly, consisting of a wheel which is joined to an exducer. These components are mechanically joined by pressing a crush ring into annulus grooves located on the mating faces. Wear of the annulus necessitates replacement of a significant quantity of the wheels during repair of the turbine rotor assemblies.

This paper discusses the development and evaluation of a repair for the annulus in the radial turbine wheel. The repair process includes heat treatment of the turbine wheel, machining the worn groove, buildup of the groove location with weld, age heat treatment, machining, and inspection. The evaluation includes microstructural examination of the repaired area, mechanical property testing of specimens from repaired wheels, and component testing of a repaired turbine rotor assembly.
In-Situ Soot Measurements in an Operating Engine Gas Turbine Combustor
Authors: Koch R. , Wittig S. , Feld H.-J. , Mohr H.-J.
Published: March 2015

The dispersion quotient method, an optical measuring technique for particles, has been applied to in situ measurements of the soot particle size and density in the secondary zone of a KHD GT-216 gas turbine combustor under operating engine conditions. The optical technique, which has been developed at the Institut of Thermische Strömungsmaschinen, is based on the light extinction at different wavelength by a particle cloud due to absorption and scattering. It is of particular advantage in applications, where particles of small size (d ≤ 1.0μ) and high density are to be investigated.

In the present investigation, two idling running conditions of the turbine have been studied: 30.000 rpm and 47.000 rpm. The results show, that the dispersion quotient method is well suited for soot measurements in pressurized flames. In particular, it was found, that the soot particle diameter is not effected by the rotating speed of the turbine. The size of the soot particles was always in the range from 0.1 to 0.3 mircon. The soot volume fraction, however, was found to be strongly influenced by different rotating speeds, with higher rotating speed causing higher volume fraction of soot.
Unsteady Lifting Surface Theory for a Rotating Transonic Cascade of Swept Blades
Authors: Kodama Hidekazu , Namba Masanobu
Published: March 2015

A lifting surface theory is developed to predict the unsteady three-dimensional aerodynamic characteristics for a rotating transonic annular cascade of swept blades. An improved method is used to solve the integral equation for the unsteady blade loading. Numerical examples are presented to demonstrate effects of the sweep on the blade flutter and on the acoustic field generated by interaction of rotating blades with a convected sinusoidal gust. It is found that, in the case of transonic rotors, the magnitude of total aerodynamic work due to the blade vibration is reduced at large sweep angles, however blade sweep is not beneficial for noise reduction.
Acoustic Emission Evaluation of Thermal Barrier Coatings Using the Three Point Bending Test
Authors: Verbeek A. T. J. , Houben J. M. , Klostermann J. A.
Published: March 2015

Thermal Barrier coatings were tested in three point bending tests, combined with acoustic emission evaluation.

The test specimens consist of a 2 mm substrate with a 0.1 mm FeCrAlY bondcoat and a 0.3 mm ZrO2/Y2O3 93/7.8 weight % topcoat. Both the topcoat and the bondcoat were air plasma sprayed under varying conditions of the substrate cooling and the length of the plasma flame.

On investigating the microstructure of the coatings, using light and electron microscopy, differences could be observed, due to the various spraying techniques.

The coated specimens were tested in a tensile testing machine equiped with a special tool for three point bending tests. During bending, acoustic emissions from the coating were measured, using a two channel acoustic emission apparatus. Two types of AE sensors were used, namely a 150 kHz resonance sensor and a 0.1 −1 MHz wide band sensor.

The various coatings show different AE patterns, especially the bondcoats which showed differences according to the spraying techniques.

The use of wide band sensors had some advantages, however they were less sensitive than resonance sensors, they take signals that were received by the resonance ones.

After testing, the specimens were prepared and microscopically investigated. Herewith it was possible to establish a relationship between the measured AE signal and the type of coating and coating failure.
Remote Condition Monitoring of a Peaking Gas Turbine
Authors: Harris Ralph E. , Simmons Harold R. , Smalley Anthony J. , Baldwin Richard M. , Quentin George
Published: March 2015

This paper illustrates how software and hardware for telecommunications and data acquisition enable cost-effective monitoring of peaking gas turbines using personal computers. It describes the design and evaluation of a system which transmits data from each start-up and shutdown over 1,500 miles to a monitoring computer. It presents system structure, interfaces, data content, and management. The system captures transient sequences of acceleration, synchronization, loading, thermal stabilization, steady operation, shutdown and cooldown; it yields coherent sets of speed, load, temperature, journal eccentricity, vibration amplitude, and phase at intervals appropriately spaced in time and speed. The data may be used to characterize and identify operational problems.
Ceramic Barrier Filters for Coal-Fueled Gas Turbine Service
Authors: Stephenson M. D. , Cowell L. H. , LeCren R. T.
Published: March 2015

Solar Turbines is developing a coal fueled version of its 3.8 MW Centaur H gas turbine for cogeneration applications. To protect gas turbine components from erosion and corrosion due to impacting particulates, and to meet New Source Performance Standards for particulate emissions, ceramic barrier filters are being employed. The test program includes evaluation of silicon carbide candle filters. Fourteen candles are being tested for 50 h at design temperature and face velocity using the particulate-laden gas stream from a two-stage slagging combustor system. The testing includes determining collection efficiency and obtaining pressure drop versus time profiles. Additionally, exposure testing is being used to determine whether loss in strength, or changes in the chemical or mineralogical structure have occurred. This includes four-point bend testing, X-ray diffraction and scanning electron microscopy with energy dispersive X-rays.
Phase Shift Torquemeters for Gas Turbine Development and Monitoring
Authors: van Millingen R. D. , van Millingen J. D.
Published: March 2015

Multipole phase shift torquemeters now measure shaft power to 0.1% accuracy in R & D applications, and to 1.0% when designed for permanent installation, both at confidence levels of 95%.

The total installed power to date is 2 million kW, and over 2 million hours have been logged with good reliability. They are in service at speeds up to 90,000 RPM and powers of 50MW.

The paper outlines ways of ensuring credibility, and describes typical designs for R & D use, and for permanent installation. It concludes that the application problems are largely those of transmission engineering.
Analytical and Experimental Determination of Tip Clearance Effects in a High Work Turbine Rotor
Authors: Liu Jong-Shang , Minkkinen George , Bozzola Riccardo
Published: March 2015

Analytical and experimental investigations were conducted to study important tip clearance flow phenomena, such as leakage vortex, flow underturning, and the effect of clearance flow on blade loading and losses. A three-dimensional Navier-Stokes code was modified to include a tip clearance model. A recently designed transonic high-work turbine rotor was used as a test case. Detailed measurements were made at rotor inlet and exit planes and compared to analytical results. The comparisons included important design features, such as exit total pressure and flow angle. For tip clearance calculation, the agreement with data was improved in the near-tip region compared to calculation without tip clearance. The clearance flow phenomena, leakage vortex, flow underturning, changing of blade loading, and loss distribution were predicted.
Euler Flow Predictions for an Oscillating Cascade Using a High Resolution Wave-Split Scheme
Authors: Huff Dennis L. , Swafford Timothy W. , Reddy T. S. R.
Published: March 2015

A compressible flow code that can predict the nonlinear unsteady aerodynamics associated with transonic flows over oscillating cascades is developed and validated. The code solves the two-dimensional, unsteady Euler equations using a time-marching, flux-difference splitting scheme. The unsteady pressures and forces can be determined for arbitrary input motions, although this paper will only address harmonic pitching and plunging motions. The code solves the flow equations on a H-grid which is allowed to deform with the airfoil motion. Predictions are presented for both flat plate cascades and loaded airfoil cascades. Results are compared to flat plate theory and experimental data. Predictions are also presented for several oscillating cascades with strong normal shocks where the pitching amplitudes, cascade geometry and interblade phase angles are varied to investigate nonlinear behavior.
Combination of Different Unsteady Quantity Measurements for Gas Turbine Blade Fault Diagnosis
Authors: Loukis E. , Wetta P. , Mathioudakis K. , Papathanasiou A. , Papailiou K.
Published: March 2015

The exploitation of different unsteady quantity measurements for identifying various blade faults is examined in this paper. Measurements of sound emission, casing vibration, shaft displacement and unsteady inner wall pressure are considered. It is demonstrated that particular measurements are sensitive to specific faults. The suitability of measuring each of the above physical quantities for tracing the existence of each kind of fault is discussed. The advantage of combining different measurements originates from the possibility of extending the fault repertory covered when only one particular quantity is considered. The data analysis techniques employed range from conventional signal processing to the derivation of acoustic images of the engine outer surface. Relative features of each technique, as to their effectiveness and level of intrusivity, are discussed.
An Integrated Gas Turbine-Kalina Cycle for Cogeneration
Authors: Olsson E. , Desideri U. , Stecco S. S. , Svedberg G.
Published: March 2015

A number of studies have shown that the Kalina cycle, using an ammonia-water mixture, can reach higher efficiencies than the normal steam Rankine cycle. In this paper, the Kalina cycle, with a gas turbine topping cycle is applied to cogeneration for district heating. Since the district heating temperatures vary with the heat demand over the year, this application may prove to be especially suitable for the Kalina cycle with its many degrees of freedom in the condensation system.

A theoretical comparison between different bottoming cycles producing heat for a typical Scandinavian district heating network has been carried out. The Kalina cycle, the Rankine cycle with a mixture of ammonia and water as the working fluid and the normal single pressure steam Rankine cycle are compared. It is shown that a simple Rankine cycle with an ammonia-water mixture as the working fluid produces more heat and power than the steam Rankine cycle. The best results, however, are obtained for the Kalina cycle, which generates considerably higher heat and power output than the steam Rankine cycle.
A Direct Optimization Procedure for Spanwise Work Distribution in Non-Free Vortex Turbine Stages
Authors: Jenkins Rhonald M.
Published: March 2015

This paper describes a technique for finding the radial distributions of flow angle and stage specific work which yield, subject to user-specified constraints, the maximum value of integrated adiabatic efficiency for a turbine stage. The optimization procedure is direct in that the distributions are specified as polynomials. A pattern search is employed to determine the values of the polynomial coefficients which yield the desired conditions. The overall technique is intended to supplement the preliminary phase of axial flow gas turbine design.
A Coal-Water Slurry Combustor for a 5MW Industrial Gas Turbine
Authors: Wilkes C. , Santanam C. B.
Published: March 2015

This paper summarizes 1/10 scale combustor test results and design parameters that have lead to the fabrication, assembly and test of a full-scale, 22 MW thermal-input (76 mmbtu/hr) combustor and engine system. The engine is a production Allison 501-K industrial turbine that has been modified to accept an external combustor designed for burning coal-water-slurry (CWS) fuel. The combustor utilizes rich-quench-lean (RQL) staging to control emissions of both thermal NOx and NOx formed from nitrogenous compounds contained in the coal-water slurry. Water is injected into the quench zone to freeze molten ash that is formed in the rich zone. The dry ash is removed from the system and collected in storage vessels by passing the hot combustion products through parallel cyclone separators. The cleaned fuel-rich gases pass to the lean zone where the addition of compressor-discharge air results in auto-ignition of the gas mixture and provides sufficient oxygen for completion of the combustion reactions.

Measurements made of emissions from the bench-scale combustor at simulated power conditions show that NOx and CO concentrations of less than 50 ppmvd corrected to 15% oxygen can be expected. Check out testing of the full-scale combustor on CWS and the combined combustor/engine assembly on distillate fuel are now in progress. It is anticipated that engine testing on CWS will commence in early 1991.
Reliability Analysis of Ceramic Matrix Composite Laminates
Authors: Thomas David J. , Wetherhold Robert C.
Published: March 2015

At a macroscopic level, a composite lamina may be considered as a homogeneous orthotropic solid whose directional strengths are random variables. Incorporation of these random variable strengths into failure models, either interactive or non-interactive, allows for the evaluation of the lamina reliability under a given stress state. Using a non-interactive criterion for demonstration purposes, laminate reliabilities are calculated assuming previously established load sharing rules for the redistribution of load as the failure of laminae occur. The matrix cracking predicted by ACK theory is modelled to allow a loss of stiffness in the fiber direction. The subsequent failure in the fiber direction is controlled by a modified bundle theory. Results using this modified bundle model are compared with previous models which did not permit separate consideration of matrix cracking, as well as to results obtained from experimental data.
Prediction of Gas Turbine On- and Off-Design Performance When Firing Coal-Derived Syngas
Authors: Johnson Mark S.
Published: March 2015

This paper describes a procedure used to model the performance of gas turbines designed to fire natural gas (or distillate oil) when fired on medium-BTU fuel, such as coal-derived syngas. Results from such performance studies can be used in the design or analysis of Gasification Combined-Cycle (GCC) power plants. The primary difficulty when firing syngas in a gas turbine designed for natural gas is the tendency to drive the compressor toward surge. If the gas turbine has sufficient surge margin and mechanical durability, Gas Turbine Evaluation code (GATE) simulations indicate that net output power can be increased on the order of 15% when firing syngas due to the advantageous increase in the ratio of the expander-to-compressor mass flow rates. Three classes of single-spool utility gas turbines are investigated spanning firing temperatures from 1985 F to 2500 F (1358 K to 1644 K). Performance simulations at a variety of part-load and ambient temperature conditions are described; the resulting performance curves are useful in GCC power plant studies.
CFD Analysis of Jet Mixing in Low NOx Flametube Combustors
Authors: Talpallikar M. V. , Smith C. E. , Lai M. C. , Holdeman J. D.
Published: March 2015

The Rich-burn/Quick-mix/Lean-burn (RQL) combustor has been identified as a potential gas turbine combustor concept to reduce NOx emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NOx levels, cylindrical flametube versions of RQL combustors are being tested at NASA Lewis Research Center. A critical technology needed for the RQL combustor is a method of quickly mixing by-pass combustion air with rich-burn gases.

In this study, jet mixing in a cylindrical quick-mix section was numerically analyzed. The quick-mix configuration was five inches in diameter and employed twelve radial-inflow slots. The numerical analyses were performed with an advanced, validated 3-D Computational Fluid Dynamics (CFD) code named REFLEQS. Parametric variation of jet-to-mainstream momentum flux ratio (J) and slot aspect ratio was investigated. Both non-reacting and reacting analyses were performed.

Results showed mixing and NOx emissions to be highly sensitive to J and slot aspect ratio. Lowest NOx emissions occurred when the dilution jet penetrated to approximately mid-radius. The viability of using 3-D CFD analyses for optimizing jet mixing was demonstrated.