bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Analytical Redundancy to the Detection of Sensor Faults on a Turbofan Engine
Authors: Kelly Ronald W.
Published: February 2015

In current generations of aero-engines the need to ensure the reliability of sensor measurements is met by using two or more sensors to read the same engine parameter. This technique is known as “hardware redundancy” and although reliable it does increase the cost of the sensor suite and also the weight of the engine. With the increasing computing power being fitted to new engines the opportunity has arisen of using “analytical redundancy” instead. Here the outputs of a software model of the engine are used to validate the real sensor outputs. Analytical redundancy divides into two main parts: the detection of a fault on a sensor, and the reconfiguration of the control system in response to this fault. The work conducted at DRA Pyestock has concentrated on the detection of sensor faults. The method employed uses a correlation approach to compare the shapes of the signals from the sensor and model. The sensor is declared to be faulty if the shapes become too dissimilar. Sea-level static engine trials have been conducted at Pyestock in which different faults were added to the sensor outputs of a Spey turbofan engine. The results were encouraging and indicated that such a fault detection approach could form part of a practical analytical redundancy scheme.
Government/Industry Partnership: A Revolutionary Approach in Global Leadership of Advanced Gas Turbines
Authors: Ali Sy A. , Zeh Charles M.
Published: February 2015

The U.S. Department of Energy (DOE) has established a government/industry partnership program to greatly improve the capabilities of U.S. gas turbine technology. A new and challenging program named the Advanced Turbine Systems Program (ATS) has been initiated by DOE. The technical and business objectives of this initiative are to challenge the bounds of high performance capabilities of gas turbines, meet stringent environmental requirements, and produce lower cost electric power and cogeneration steam. This program will also yield greater societal benefits through continued expansion of high skilled U.S. jobs and export of U.S. products world wide.

A progress report on the ATS program pertaining to program status at DOE will be presented and reviewed in this paper. A preliminary design of an industrial advanced turbine system configuration will also be outlined in the paper. The technical challenges; advanced critical technologies incorporation, analytical and experimental solutions, and test results of an advanced gas turbine meeting the DOE goals will be described and discussed.
Free Vibration of a Rotating Disk–Blade Coupled System With Shrouds
Authors: Kobayashi Yukinori , Yamada Gen , Tomioka Takahiro
Published: February 2015

The free vibration of rotating disk–blade coupled system is investigated by the Ritz method. Centrifugal effects due to rotation are taken into account for both of the disk and blades. The boundary and continuity conditions between the disk and blades are satisfied by means of artificial springs introduced at their joints, and the orthogonal polynomials generated by using the Gram–Schmidt process are employed as admissible functions for both of the disk and blades. Frequency parameters and mode shapes of vibration are obtained to investigate the vibration of the disk–blade coupled system.
Dry Low NOx Combustion Systems for GE Heavy-Duty Gas Turbines
Authors: Davis L. Berkley
Published: February 2015

General Electric began development of Dry Low NOx (DLN) systems in the mid-1970s and operated its first DLN system in 1981 (Reference 1). Subsequent to that, further development was done (Reference 2) prior to commercial introduction.
Comparison of a TVD-Upwind Scheme and a Central Difference Scheme for Navier-Stokes Turbine Stage Flow Calculation
Authors: Raif Markus , Mayer Jürgen F. , Stetter Heinz
Published: February 2015

The differences of two distinct numerical schemes implemented in one code called ITSM3D are presented for a turbine stage test case. Thus both schemes are used with exactly the same computational infrastructure, e. g, same grids, boundary conditions, acceleration strategies, time-stepping, turbulence model etc. The two methods are based on an explicit Runge-Kutta-type finite volume scheme expressed in cylindrical coordinates and have been developed at the Institut für Thermische Strömungsmaschinen und Maschinenlaboratorium of the University of Stuttgart. One scheme is a node centered 3rd order TVD scheme according to Osher and the other belongs to the cell vertex central difference type with the concept of artificial viscosity. The model of Baldwin-Lomax is used in order to simulate turbulent effects. Non-reflective boundary conditions are taken at stator inlet and rotor outlet to avoid non-physical reflections. A multigrid technique in combination with implicit residual smoothing and local time-stepping is employed to accelerate the computation.

The test case for this comparison is the last stage of a low-pressure turbine. The computational results obtained are discussed and compared to each other as well as to experimental data. They are presented as pressure and Mach number isoline contours and diagrams of circumferential averaged quantities at inlet and outlet planes of stator and rotor versus radial position.
Status of the Automotive Ceramic Gas Turbine Development Program: Year Five Progress
Authors: Nisiyama Tsubura , Nakazawa Norio , Sasaki Masafumi , Iwai Masumi , Katagiri Haruo , Handa Noritoshi
Published: February 2015

Petroleum Energy Center of Japan has been carrying out a 7-year development program to prove the potential of an automotive ceramic gas turbine for five years with the support of the Ministry of International Trade and Industry. The ceramic gas turbine now under development is a regenerative single shaft engine. The output is 100kW, and the turbine inlet temperature (TIT) is 1350°C.

All the ceramic components are now entering the 1350°C TIT test phase after completing 1200°C TIT evaluation tests, including durability tests, in various types of test rigs. The compressor-turbine combined test rig and the full assembly test rig which is the same as an actual engine and incorporates all the components are now going through 1200°C TIT function and performance evaluation tests. In the near future, we are planning to increase the TIT to 1350°C.

In consideration of the current level of high-temperature, long-term strength available from the ceramic materials, we decided to change the rated speed to 100,000 rpm because the initial rated speed of 110,000 rpm, if unchanged, involves considerable risks. Then we reviewed mainly the designs of the compressor and turbine and revised the target values of the individual components to match the specifications that satisfy the target performance of the engine.
Detailed Velocity and Turbulence Measurements of the Profile Boundary Layer in a Large Scale Turbine Cascade
Authors: Ubaldi Marina , Zunino Pietro , Campora Ugo , Ghiglione Andrea
Published: February 2015

Extensive measurements of velocity and turbulence have been performed by means of a two-component fibre-optic laser Doppler velocimeter, to investigate the profile boundary layer development on a large scale turbine cascade.

Flow field investigation has been integrated with data obtained by surface-mounted hot-film gauges in order to get direct information on the boundary layer nature and on its time varying characteristics.

Measurements were detailed enough to allow constructing mean velocity and Reynolds stress boundary layer profiles giving an in-depth description of the boundary layer development along both suction and pressure surfaces through laminar, transitional and turbulent regimes.
Development of a Small Low NOx Combustor With a Staging System for an Aircraft Engine: Part 1
Authors: Kobayashi Masayoshi , Arai Masashi , Kuyama Toshiyuki
Published: February 2015

A small low NOx combustor has been developed by KHI (Kawasaki Heavy Industries Limited). To achieve low NOx and stable combustion simultaneously, a fuel nozzle test was conducted for three types of fuel nozzles, which were expected to promote an air/fuel mixing. A sector combustor lest was conducted for various combustor configurations to examine combustion performances, evaluating especially the flame propagation from the pilot to the main stage. As a result of these tests, much useful design data for the combustor were obtained.
Techniques to Characterize the Thermal-Oxidation Stability of Jet Fuels and the Effects of Additives
Authors: Vilimpoc V. , Sarka B. , Weaver W. L. , Gord J. R. , Anderson S.
Published: February 2015

Three techniques integrated into a single instrumented platform allow simultaneous measurement in real time of particle-size growth rate, surface mass-deposition rate, and concentration of dissolved oxygen in thermally stressed jet fuel. Particle growth rate is studied using Photon Correlation Spectroscopy (PCS); surface mass-deposition rate is measured with a Quartz Crystal Microbalance (QCM); and dissolved-oxygen concentration is monitored by Pyrene Fluorescence Quenching (PFQ). The three techniques have been used simultaneously to study the behavior of a jet fuel undergoing thermal stressing and to evaluate the performance of an anti-oxidant, a dispersant, and a metal deactivator in another jet fuel.
An Advanced Development of a Second-Generation Dry, Low-NOx Combustor for 1.5MW Gas Turbine
Authors: Kajita Shin-ichi , Ohga Shin-ichi , Ogata Masahiro , Itaka Satoru , Kitajima Jun-ichi , Kimura Takeshi , Okuto Atsushi
Published: February 2015

Advanced development of a second-generation dry, low-NOx combustor for KHI’s 1.5MW industrial gas turbine, M1A-13A, is described. In this advanced development, efforts were made mainly to improve combustion efficiency in addition to NOx reduction experimentally. The combustion liner was extended to increase combustion volume, and supplemental burners were installed downstream of multiple main burners to broaden low-NOx operation range. In consequence of the optimization of the fuel allotment, air/fuel ratio at each burner, cooling air, and so on, the engine showed NOx emissions under 15 ppm (15% O2), and a combustion efficiency more than 99.5% over the range between 75% and 100% load. Finally, by means of a 300-hour operation at full load and a 500-cycle endurance test, the total reliability of this combustion system was ensured.
Excited Turbulent Reacting Flows in a Chamber With Gaseous Fuels Injecting Through Porous Walls
Authors: Liou Tong-Miin , Hwang Po-Wen , Lien Wan-Yih
Published: February 2015

A numerical analysis was performed to study excited turbulent reacting flows in a combustion chamber consisting of gaseous fuels injecting through porous walls. The time-dependent axisymmetric compressible conservation equations were solved directly without using subgrid-scale turbulence models. The combustion process considered was a one-step, irreversible, and infinitely fast chemical reaction. The numerical code used the finite-volume technique, which involved alternating in time the second-order, explicit MacCormack’s and modified Godunov’s schemes. Excitations with various forcing frequencies were applied to the air inflow boundary to investigate their effects on the large-scale unsteady flow structures, vorticity dynamics, mean flame position, mean temperature distribution, and characteristic exhaust velocity.

From the numerical flow visualization of the instantaneous vorticity field and the associated vorticity dynamics analysis, a rationale for the augmentation or diminution of organized vortical structures under external excitations was provided. It is found that an excitation with the fundamental frequency attains a larger high temperature recirculation zone with a higher peak temperature and hence a better flame-holding condition. An application of the active control by forcing the air inlet velocity with the fundamental frequency at various amplitudes to an original non-sustained combustion case indicates that the combustion can be sustained if an appropriate exciting amplitude is selected.
Development of a Dry Low NOx Combustor for 2MW Class Gas Turbine
Authors: Hosoi J. , Watanabe T. , Toh H. , Mori M. , Sato H. , Ishizuka A.
Published: February 2015

Development of a dry low NOx combustor for 2MW class gas turbine is described, which has been co-conducted by Ishikawajima-Harima Heavy Industries Co., Ltd. and Tokyo Gas Co., Ltd. from 1994. This combustor is characterized by three stage, lean premixed combustion with coaxial burners operated by simple control system and non-film cooling, from which low NOx and high combustion efficiency within the wide region of load can be obtained. Component rig tests indicated NOx ≒10ppm (at 16% O2), combustion efficiency η c >99.8% could be obtained over load more than 50%.
Design and Development of a Two Stage Transonic Axial Flow Compressor
Authors: Nagai Katsushi , Ikesawa Kazuaki , Sugimoto Takao , Tanaka Toshinao , Umino Hiroshi , Ryuguji Takeshi
Published: February 2015

A highly loaded two stage transonic axial flow compressor, which forms a front stages of a multi stage compressor for industrial gas turbines, has been designed and tested. Overall pressure ratio is 2.25 and the first stage rotor tip Mach number is 1.15. Two airfoil types, Double Circular Arc airfoil and Multi Circular Arc airfoil, were designed for a transonic rotor blade under the same condition. MCA blade design method was devised and introduced. The blade design relied heavily on CFD techniques using a Euler code and a Navier Stokes code to cope with a precise treatment. The rig test was conducted by our compressor test facility to verify a validity of the transonic compressor design method and to compare the performance of the DCA and the MCA airfoils. This report describes the aerodynamic design and the test results as well as the test facility and instrumentation.
The Influence of Inlet Swirl on the Flow Within an Annular S-Shaped Duct
Authors: Bailey D. W. , Carrotte J. F.
Published: February 2015

An experimental investigation has been carried out to determine the effects of inlet swirl on the flow field that develops within an annular S-shaped duct. The duct is representative of that used to connect the compressor spools on multi-spool gas turbine engines. By removing the outlet guide vanes from an upstream single stage compressor swirl angles in excess of 30° were generated. Results show that within the S-shaped duct tangential momentum (Wr) is conserved, leading to increasing swirl velocities through the duct as the radius decreases. Furthermore, this component influences the streamwise velocity as pressure gradients are established to ensure the mean flow follows the duct curvature. Consequently in the critical region adjacent to the inner casing, where separation is likely to occur, higher streamwise velocities are observed. Within the duct substantial changes also occur to the turbulence field which results in an increased stagnation pressure loss between duct inlet and exit. Data is also presented showing the increasing swirl angles through the duct which has consequences both for the design of the downstream compressor spool and of any radial struts which may be located within the duct.
Compressor Off-Design Performance Prediction Using an Endwall Model
Authors: Dunham John
Published: February 2015

A throughflow method for designing and analysing compressors has to be supplied with loss, deviation, and blockage estimates for every blade row. The earliest methods used empirical correlations for profile loss and deviation, together with an empirical blockage or “work done” factor, and empirical estimates of additional losses near the endwalls. Previous papers by the author have described how to replace the empirical blockage factor and endwall corrections by explicit calculations using a new mathematical model of the endwall phenomena. Those papers illustrated the application of the method near design conditions, using either design profile loss and deviation figures or computations by a viscous-inviscid interaction blade-to-blade method.

In order to estimate off-design performance rapidly over the whole operating range, some way of estimating off-design profile loss and deviation must be chosen. In this paper, the previously-derived design point loss and deviation figures are retained, and an empirical correlation due to Miller, Wasdell, and Wright is used to predict the changes in loss and deviation off-design. It is shown by means of sample three-dimensional Navier-Stokes computations that the endwall model remains applicable off-design.

The method has been tested against two low speed and two high speed compressors, one of each example having controlled-diffusion blading. The low speed compressor characteristic maps are predicted only approximately, but the predicted high speed compressor maps are good. It is widely believed that endwall flow separation can initiate stall or surge. As stall or surge was approached the shape factor of the annulus wall boundary layer at one location rose sharply, but no single stall-predicting value could be found.
The Application of a Computer-Aided Design Technique to the Conceptual Design of Turbochargers: Part A — Centrifugal Compressor Design and Turbine Matching
Authors: Whitfield A. , Abdullah Abu Hasan
Published: February 2015

In many turbomachinery applications a compressor is directly driven by a turbine; for turbocharger applications a centrifugal compressor is usually adopted which is generally driven by a radial flow turbine, although mixed flow or axial flow turbines are occasionally required. A non-dimensional design procedure is developed to provide the basic dimensions and blade angles of centrifugal compressor impellers, whilst accounting for the turbine conditions as assessed through the matching requirements. The design of the turbine is then considered further in Part B.

The procedure can be applied for any desired compressor pressure ratio and target efficiency to develop an initial non-dimensional skeleton design. No other parameters are required from the initial specification and the design is developed non-dimensionally without recourse to empirical loss models and the associated uncertainties as the target efficiency must be specified. The procedure provides graphical information with respect to the impeller discharge conditions and inlet conditions from which the designer must select the most appropriate design. The screen graphics interface enables the designer to search across the design options; as this search is carried out numerical data are displayed and continuously up-dated to provide immediate information on which an infnrmed assessment can be based.

In addition to the compressor design options which are provided the matching conditions for the drive turbine provides information, such as specific speed, non-dimensional mass flow rate and pressure ratio, relevant to the turbine design. Judgements with respect to the design options for the compressor can then be made with the consequences for the associated turbine design clearly in view.

The non-dimensional design can be translated into an absolute design through the specification of the required mass flow rate and the inlet stagnation pressure and temperature.
The Application of a Computer-Aided Design Technique to the Conceptual Design of Turbochargers: Part B — Radial Turbine Design
Authors: Whitfield A. , Abdullah Abu Hasan
Published: February 2015

A procedure similar to that presented in Part A is described for the non-dimensional design of radial inflow turbines. The technique is developed non-dimensionally to provide the overall dimensions, including the leading and trailing edge blade angles, of radial flow turbine rotors. Consideration of the adoption of non-radial blades at rotor inlet, leading to mixed flow rotors, and discharge swirl is included.

The procedure is developed from a knowledge of the non-dimensional power requirement which is derived through the turbocharger matching conditions. To satisfy the matching requirement the mechanical efficiency of the turbocharger, the air fuel ratio, the inlet stagnation temperature relative to that at compressor inlet, and the gas constants for the hot exhaust gas must be specified. In addition a target stage efficiency, on a total to static basis, must be specified.

In essence the procedure provides graphically all the possible velocity vectors at rotor inlet and exhaust. The graphical presentation allows the designer to survey all the options available; as this is done relevant data is presented and continuously up-dated to aid in the selection of the preferred design conditions.

The non-dimensional geometry of the rotor is then developed from which the absolute dimensions can be derived through the specification of the gas mass flow rate and the inlet stagnation conditions.
Numerical Calculations of a Turbine Volute Using a 3-D Navier-Stokes Solver
Authors: Martinez-Botas R. F. , Pullen K. R. , Shi F.
Published: February 2015

The turbine volute is a complex flow device, about which a few papers on both measurements and CFD predictions have appeared. The main reasons for the difficulties being the complicated geometry which hinders measurements to be taken by both intrusive and non-intrusive techniques, and makes the numerical predictions difficult.

In this paper, the complex three-dimensional flow through a turbine volute with non-symmetric circular cross-section is studied by using a 3-D Navier-Stokes solver which has been developed by the authors. In this solver, the fully 3-D Reynolds averaged N-S equations coupled with high Reynolds number k-ε turbulence model together with the wall function under arbitrary curvilinear coordinate system are solved. The Semi-Implicit Method for Pressure-Linked Equations (SIMPLEC algorithm) with the non-staggered grid arrangement is used. In order to eliminate the decoupling between the velocity and pressure under non-staggered grid system, the physical covariant velocity component is selected as dependent variable in momentum equations and a momentum interpolation approach is employed.

The validity of the free-vortex assumption is reviewed. The computation results are compared with a set of experiments performed previously by one of the authors. The flow features in the volute are discussed.
Performance Benefits for Wave Rotor-Topped Gas Turbine Engines
Authors: Jones Scott M. , Welch Gerard E.
Published: February 2015

The benefits of wave rotor-topping in turboshaft engines, subsonic high-bypass turbofan engines, auxiliary power units, and ground power units are evaluated. The thermodynamic cycle performance is modeled using a one-dimensional steady-state code; wave rotor performance is modeled using one-dimensional design/analysis codes. Design and off-design engine performance is calculated for baseline engines and wave rotor-topped engines, where the wave rotor acts as a high pressure spool. The wave rotor-enhanced engines are shown to have benefits in specific power and specific fuel flow over the baseline engines without increasing turbine inlet temperature. The off-design steady-state behavior of a wave rotor-topped engine is shown to be similar to a conventional engine. Mission studies are performed to quantify aircraft performance benefits for various wave rotor cycle and weight parameters. Gas turbine engine cycles most likely to benefit from wave rotor-topping are identified. Issues of practical integration and the corresponding technical challenges with various engine types are discussed.
Coal/Biomass Fuels and the Gas Turbine: Utilization of Solid Fuels and Their Derivatives
Authors: DeCorso Mario , Newby Richard , Anson Don , Wenglarz Richard , Wright Ian
Published: February 2015

This paper discusses key design and development issues in utilizing coal and other solid fuels in gas turbines. These fuels may be burned in raw form or processed to produce liquids or gases in more or less refined forms. The use of such fuels in gas turbines requires resolution of technology issues which are of little or no consequence for conventional natural gas and refined oil fuels. For coal, these issues are primarily related to the solid form in which coal is naturally found and its high ash and contaminant levels. Biomass presents another set of issues similar to those of coal. Among the key areas discussed are effects of ash and contaminant level on deposition, corrosion, and erosion of turbine hot parts, with particular emphasis on deposition effects.
Empirical and Semi-Empirical Correlation of Emissions Data From Modern Turbopropulsion Gas Turbine Engines
Authors: Danis Allen M. , Pritchard Byron A. , Mongia Hukam C.
Published: February 2015

The engine certification emissions data from a CFM56 single-annular combustor (SAC), the CFM56 dual-annular combustor (DAC), the CF6-80C SAC and the CF6-80C SAC low-emissions configuration (LEC) were used to show the following:

(1) NOxEI can be correlated as a function of P3 and T3.

(2) There is a unique relationship between NOx, CO and unburned hydrocarbons (HC).

(3) NOx, CO and HC for engine operating points can be predicted reasonably well through “single reactor” modeling. However, the resulting NOx/CO/HC relationship is not as well predicted indicating need for further improving the semiempirical methodology.
Performance Modeling of Aeroderivative Steam-Injected Gas Turbines and Combined Cycles Fueled From Fixed or Fluid-Bed Biomass Gasifiers
Authors: Larson Eric D. , Hughes Wendy E. M.
Published: February 2015

First-generation biomass integrated-gasifier/gas turbine (BIG/GT) technology, based on combined cycles and fluid-bed gasifiers, is likely to be commercially ready by the turn of the century, with ten or more commercially-oriented demonstration projects presently ongoing worldwide. In development and demonstration efforts to date, relatively little attention has been given to alternative cycle configurations or gasifier designs. Performance modeling is described here for steam-injected and combined cycle systems built around gas turbines resembling the GE LM2500, with fuel delivered from integrated fluid- or fixed-bed gasifiers. Some features of fixed-bed gasification appear to offer benefits, particularly for steam-injected cycles. A primary motivation for examining steam injection is expected capital cost savings compared to combined cycles, especially at total power plant capacities below 100 MW. (due to scale economies associated with steam bottoming cycles). Because of the inherently dispersed nature of biomass production, first-generation BIG/GT applications in the sub-100 MW. range will be common.
Effect of Check Valve Dynamics on the Sizing of Recycle Systems for Centrifugal Compressors
Authors: Botros K. K. , Richards D. J. , Roorda O.
Published: February 2015

A recycle system for centrifugal compressors is designed to minimize the potential for surge, as can occur during shut down of the compressor. The recycle system volume capacitance (V) and the recycle valve capacity (Cg) are sized to give the required system dynamic response for surge prevention. Thusfar the check valve dynamic characteristic was not taken into account in the sizing of the recycle system. A numerical investigation was carried out on a scaled-down model of a compressor station to study the dynamic behavior of the check valve in relation to the recycle valve capacity (Cg), its dynamic characteristics, and the recycle system volume capacitance (V) during an emergency shutdown (ESD) of the compressor unit. A model describing the dynamic characteristics of an undamped check valve was introduced into the dynamic simulation of the entire system during ESD. The results show that the sizing of the recycle system can be optimized by also taking into account the check valve dynamic characteristics. Furthermore, it was found that Cg is proportional to the logarithm of the slope of the check valve dynamic characteristics, demonstrating that a small increase or decrease in Cg could have a dramatic effect on the maximum allowable reverse flow through the check valve without surging the compressor during ESD. The recycle piping volume (V), however, was found to be linearly proportional to the slope of the check valve dynamic characteristics resulting in a less dramatic effect. This paper presents numerical results and a discussion of these relationships.
Radial Compressor Fault Identification Using Dynamic Measurement Data
Authors: Aretakis N. , Mathioudakis K.
Published: February 2015

The exploitation of different unsteady quantity measurements for identifying mechanical alterations on a radial compressor with a vaned diffuser is examined in this paper. Measurements of sound emission, casing vibration and unsteady inner wall pressure are performed. The mechanical alterations considered have been chosen in order to reproduce or simulate faults in the compressor. They include the insertion of an inlet obstruction, an obstruction in a diffuser passage, variation of impeller tip clearance, and impeller fouling. Processing these measurement data leads to the derivation of fault signatures which can be utilized for identifying them. The suitability of measuring each of the above physical quantities is discussed with respect to their sensitivity to particular faults. The dependence of the fault signatures on operating point is also examined. It’s demonstrated that minor faults which do not affect compressor operation and are not detectable by performance monitoring, can possibly be detected by the proposed methodology.
Transition of a Technology Base for Advanced Aircraft Gas Turbine Control Systems
Authors: McGlone Michael E.
Published: February 2015

Technology assessments during the 1980’s projected the development of advanced military fighter aircraft which would require propulsion systems which could accommodate multi-mission capability with super maneuverability. These propulsion systems would be required to provide significantly improved thrust to weight, reduced thrust specific fuel consumption, and up and away thrust vectoring capabilities. Digital electronic control systems with significantly expanded capabilities would be required to handle these multi-function control actuation systems, integration with flight control systems, and to provide fail-operational capability.

This paper will discuss the challenges that were presented to propulsion system control designers, the innovation of technology to address these challenges, and the transition of that technology to production readiness. Technology advancements will be discussed in the area of digital electronic control capability and packaging, advanced fuel management systems, high pressure fuel hydraulic actuation systems for multi-function nozzles, integrated flight propulsion controls, and higher order language software development tools. Each of these areas provided unique opportunities where technology development programs and flight prototyping carried concepts to reality.
A Normalized Modal Eigenvalue Approach for Resolving Modal Interaction
Authors: Yang Ming-Ta , Griffin Jerry H.
Published: February 2015

Modal interaction refers to the way that the modes of a structure interact when its geometry and material properties are perturbed. The amount of interaction between the neighboring modes depends on the closeness of the natural frequencies, the mode shapes, and the magnitude and distribution of the perturbation. By formulating the structural eigenvalue problem as a normalized modal eigenvalue problem, it is shown that the amount of interaction in two modes can be simply characterized by six normalized modal parameters and the difference between the normalized frequencies. In this paper, the statistical behaviors of the normalized frequencies and modes are investigated based on a perturbation analysis. The results are independently verified by Monte Carlo simulations.
A Numerical Investigation of the Startup Transient in a Wave Rotor
Authors: Paxson Daniel E.
Published: February 2015

The startup process is investigated for a hypothetical four-port wave rotor, envisioned as a topping cycle for a small gas turbine engine. The investigation is conducted numerically using a multi-passage, one-dimensional CFD based wave rotor simulation in combination with lumped volume models for the combustor, exhaust valve plenum, and rotor center cavity components. The simulation is described and several startup transients are presented which illustrate potential difficulties for the specific cycle design investigated. In particular it is observed that, prior to combustor light-off, or just after, the flow through the combustor loop is reversed from the design direction. The phenomenon is demonstrated and several possible modifications techniques are discussed which avoid or overcome the problem.
Aerodynamically Induced Radial Forces in a Centrifugal Gas Compressor: Part 1 — Experimental Measurement
Authors: Moore J. Jeffrey , Flathers Michael B.
Published: February 2015

Net radial loading arising from asymmetric pressure fields in the volutes of centrifugal pumps during off-design operation is well known and has been studied extensively. In order to achieve a marked improvement in overall efficiency in centrifugal gas compressors, vaneless volute diffusers are matched to specific impellers to yield improved performance over a wide application envelope. As observed in centrifugal pumps, nonuniform pressure distributions that develop during operation above and below the design flow create static radial loads on the rotor. In order to characterize these radial forces, a novel experimental measurement and post-processing technique is employed that yields both the magnitude and direction of the load by measuring the shaft centerline locus in the tilt-pad bearings. The method is applicable to any turbomachinery operating on fluid film radial bearings equipped with proximity probes. The forces are found to be a maximum near surge and increases with higher pressures and speeds. The results are nondimensionalized allowing the radial loading for different operating conditions to be predicted.
Fuel Nozzle Aerodynamic Design Using CFD Analysis
Authors: Crocker D. Scott , Fuller Eric J. , Smith Clifford E.
Published: February 2015

The aerodynamic design of airflow passages in fuel injection systems can be significantly enhanced by the use of CFD analysis. Attempts to improve the efficiency of the fuel nozzle design process by using CFD analyses have generally been unsuccessful in the past due to the difficulties of modeling swirling flow in complex geometries. Some of the issues that have been obstacles to successful and timely analysis of fuel nozzle aerodynamics include grid generation, turbulence models, and definition of boundary conditions. This study attempts to address these obstacles and demonstrate a CFD methodology capable of modeling swirling flow within the internal air passages of fuel nozzles. The CFD code CFD-ACE was used for the analyses. Results of non-reacting analyses and comparison with experimental data are presented for three different fuel nozzles. The three nozzles have distinctly different designs (including axial and radial inflow swirlers) and thus demonstrate the flexibility of the design methodology. Particular emphasis is given to techniques involved in predicting the effective flow area (ACd) of the nozzles. Good agreement between CFD predictions of the ACd (made prior to experiments) and the measured ACd was obtained. Comparisons between predicted and measured velocity profiles also showed good agreement.
Characterization of NOx, N2O, and CO for Lean-Premixed Combustion in a High-Pressure Jet-Stirred Reactor
Authors: Steele Robert C. , Tonouchi Jon H. , Nicol David G. , Horning David C. , Malte Philip C. , Pratt David T.
Published: February 2015

A high-pressure jet-stirred reactor (HP-JSR) has been built and applied to the study of NOx and N2O formation and CO oxidation in lean-premixed (LPM) combustion. The measurements obtained with the HP-JSR provide information on how NOx forms in lean-premixed, high-intensity combustion, and provide comparison to NOx data published recently for practical LPM combustors. The HP-JSR results indicate that the NOx yield is significantly influenced by the rate of relaxation of super-equilibrium concentrations of the O-atom. Also indicated by the HP-JSR results are characteristic NOx formation rates. Two computational models are used to simulate the HP-JSR, and to provide comparison to the measurements. The first is a chemical reactor model (CRM) consisting of two perfectly-stirred reactors (PSRs) placed in series. The second is a stirred reactor model with finite rate macromixing (i.e., recirculation) and micromixing. The micromixing is treated by either coalescence-dispersion (CD) or interaction-by-exchange-with-the-mean (IEM) theory. Additionally, a model based on one-dimensional gas dynamics with chemical reaction is used to assess chemical conversions within the gas sample probe.
Structure of Airblast Sprays Under High Ambient Pressure Conditions
Authors: Zheng Q. P. , Jasuja A. K. , Lefebvre A. H.
Published: February 2015

A single-velocity-component Phase Doppler Particle Analyzer is used to survey and measure local variations in drop-size distributions and drop velocities in the near-nozzle region of a practical, contra-swirling, prefilming airblast atomizer. The technique of Laser Sheet Imaging is used to obtain global patterns of the spray. All measurements are taken with a constant pressure drop across the atomizer of 5 percent, at ambient air pressures of 1, 6 and 12 bar. The liquid employed is aviation kerosine at flow rates up to 75 g/s. The results show that increasing the air pressure from 1 to 12 bar at a constant air/fuel ratio causes the initial spray cone angle to widen from 85° to 105°. Further downstream the spray volume remains largely unaffected by variations in atomizer operating conditions. However, the radial distribution of fuel within the spray volume is such that increases in fuel flow rate cause a larger proportion of fuel to be contained in the outer regions of the spray.

The effect of ambient pressure on the overall Sauter mean diameter is small. This is attributed to the fact that the rapid disintegration of the fuel sheet produced by the contra-swirling air streams ensures that the atomization process is dominated by the ‘prompt’ mechanism. For this mode of liquid breakup, theory predicts that mean drop sizes are independent of air pressure.
Numerical Prediction of the Dynamic Behaviour of Turbulent Diffusion Flames
Authors: Bohn Dieter , Deutsch Gregor , Krüger Uwe
Published: February 2015

Environmental compatibility requires low emission burners for gas turbine power plants as well as for jet engines. In the past significant progress has been made developing low NOx and CO burners. Unfortunately these burners often have a more pronounced tendency than conventional burner designs to produce combustion driven oscillations The oscillations may be excited to such an extent that pronounced pulsation may possibly occur; this is associated with a risk of engine failure.

The stability of a burner system can be investigated by means of a stability analysis under the assumption of acoustical behaviour. The problem with all these algorithms is the transfer function of the flame. A new method is presented here to predict the dynamic flame behaviour by means of a full Navier-Stokes-simulation of the complex combustion process. The first step is to get a steady-state solution of a flame configuration. After that a transient simulation follows with a sudden change in the mass flow rate at the flame inlet. The time-dependent answer of the flame to this disturbance is then transformed into the frequency space by a Laplace Transformation. This leads, in turn, to the frequency response representing the dynamic behaviour of the flame.

In principle, this method can be adapted for both diffusion as well as premixed flame systems. However, due to the fact that diffusion flames are more controlled by the mixing process than by the chemical kinetic, the method has first been used for the prediction of the dynamic behaviour of turbulent diffusion flames. The combustion has been modelled by a mixed-is-burnt model. The influence of the turbulence has been taken into account by a modified k-ε-model and the turbulence influences the combustion rate by presumed probability density functions (pdf).

The steady-state as well as the transient results have been compared with experimental data for two different diffusion flame configurations. Although the burner configuration is relatively complex, the steady state results collaborate very well with the experiments for velocity, temperature and species distribution. The most important result is that the heat release which drives the oscillations can be modelled sufficiently accurately. The effect of using different pdf-models has been discussed and the best model has been used for the transient calculations of the dynamic flame behaviour.

The results for the frequency response of the flame are very encouraging. The principal behaviour of the flame — higher order time element with a delay time — can be predicted with sufficient precision. In addition, the qualitative results collaborate fairly well with the experiments.
Development of a Dry Ultra Low NOx Double Swirler Staged Gas Turbine Combustor
Authors: Sato Hiroshi , Mori Masaaki
Published: February 2015

This paper describes the development of an ultra-low NOx gas turbine combustor for cogeneration systems. The combustor, called a double swirler staged combustor, utilizes three-staged premixed combustion for low NOx emission. The unique feature of the combustor is its tertiary premix nozzles located downstream of the double swirler premixing nozzles around the combustor liner. Engine output is controlled by simply varying the fuel gas flow, and therefore employs no complex variable geometries for air flow control. Atmospheric combustion tests have demonstrated the superior performance of the combustor. NOx level is maintained at less than 3 ppm (O2=15%) over the range of engine output between 50% and 100%. Assuming the general relationship that NOx emission is proportional to the square root of operating pressure, the NOx level is estimated at less than 9 ppm (O2=15%) at the actual pressure of 0.91 MPa (abs.). Atmospheric tests have also shown high combustion efficiency; more than 99.9% over the range of engine output between 60% and 100%. Emissions of CO and UHC are maintained at 0 and 1 ppm (O2=15%), respectively, at the full engine load.
Application of Thermochromic Liquid Crystal to Rotating Surfaces
Authors: Camci C. , Glezer G. , Owen J. M. , Pilbrow R. G. , Syson B. J.
Published: February 2015

Encapsulated thermochromic liquid crystal (TLC) can be used to measure the surface temperature of stationary or rotating bodies. However, some research workers have reported a “rotational shift”; when the temperature of a rotating body is measured by thermocouples and TLC, there is a difference between the two sets of temperatures, and this difference increases with increasing rotational speed.

Two research groups (Camci and Glezer in the USA, and Owen, Pilbrow and Syson in the UK) have independently examined the effect of speed on TLC applied to the surfaces of rotating disks. The USA group used narrow-band TLC on a disk of 305-mm diameter rotating up to 7500 rev/min, measuring the surface temperature using an infra-red (IR) sensor. The UK group used wide-band TLC on a disk of 580-mm diameter rotating up to 7000 rev/min, measuring the temperature with an IR thermal imager. Both groups used the so-called hue technique to evaluate the temperature of the TLC and concluded that, even for centripetal accelerations in excess of 104g, there is no significant effect of rotational speed on either narrow-band or wide-band TLC. It is suggested that the “rotational shift” observed by some researchers was probably caused by thermal-disturbance errors, which affected the thermocouples, rather than by changes in the TLC.
Flow Development Through Inter-Turbine Diffusers
Authors: Dominy Robert G. , Kirkham David A. , Smith Andrew D.
Published: February 2015

Inter-turbine diffusers offer the potential advantage of reducing the flow coefficient in the following stages leading to increased efficiency. The flows associated with these ducts differ from those in simple annular diffusers both as a consequence of their high-curvature S-shaped geometry and of the presence of wakes created by the upstream turbine. Experimental data and numerical simulations clearly reveal the generation of significant secondary flows as the flow develops through the diffuser in the presence of cross-passage pressure gradients. The further influence of inlet swirl is also demonstrated. Data from experimental measurements with and without an upstream turbine are discussed and computational simulations are shown not only to give a good prediction of the flow development within the diffuser but also to demonstrate the importance of modelling the fully three-dimensional nature of the flow.
Design and Test of a New Axial Compressor for the Nuovo Pignone Heavy Duty Gas Turbines
Authors: Benvenuti Erio
Published: February 2015

This axial compressor design was primarily focused to increase the power rating of the current Nuovo Pignone PGT10 Heavy-Duty gas turbine by 10%. In addition, the new 11-stage design favourably compares with the existing 17-stage compressor in terms of simplicity and cost. By seating the flowpath and blade geometry, the new aerodynamic design can be applied to gas turbines with different power ratings as well. The reduction in the stage number was achieved primarily through the meridional flow-path redesign. The resulting higher blade peripheral speeds achieve larger stage pressure ratios without increasing the aerodynamic loadings. Wide chord blades keep the overall length unchanged thus assuring easy integration with other existing components.

The compressor performance map was extensively checked over the speed range required for two-shaft gas turbines. The prototype unit was installed on a special PGT10 gas turbine setup, that permitted the control of pressure ratio independently from the turbine matching requirements. The flowpath instrumentation included strain-gages, dynamic pressure transducers and stator vane leading edge aerodynamic probes to determine individual stage characteristics. The general blading vibratory behavior was proved fully satisfactory. With minor adjustments to the variable stator settings the front stage aerodynamic matching was optimized and the design performance was achieved.
Aircraft Gas Turbine Engine Fuel Pumping Systems in the 21st Century
Authors: Hansen Lowell D. , Kucera Gregory D. , Clemons Jeffrey S. , Lee Jinkook
Published: February 2015

Since their introduction, main engine fuel pumping systems for aircraft gas turbine engines have remained relatively unchanged. The main engine fuel pump has been an engine accessory gearbox driven, positive displacement pump (except for the Concorde), until recently when centrifugal pumps were introduced on Pratt-Whitney and General Electric military engines. This paper describes some of the issues which must be addressed as pumping system technology moves into the 21st century and gives a description of two programs which address these issues.