bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Coriolis and Turbine Type Flow Meters for Fuel Measurement in Gas Turbine Testing
Authors: MacLeod J. D. , Grabe W.
Published: February 2015

The Machinery and Engine Technology (MET) Program of the National Research Council of Canada (NRCC) has established a program for the evaluation of sensors to measure gas turbine engine performance accurately. The precise measurement of fuel flow is an essential part of steady-state gas turbine performance assessment. Prompted by an international engine testing and information exchange program, and a mandate to improve all aspects of gas turbine performance evaluation, the MET Laboratory has critically examined two types of fuel flowmeters, Coriolis and turbine. The two flowmeter types are different in that the Coriolis flowmeter measures mass flow directly, while the turbine flowmeter measures volumetric flow, which must be converted to mass flow for conventional performance analysis. The direct measurement of mass flow, using a Coriolis flowmeter, has many advantages in field testing of gas turbines, because it reduces the risk of errors resulting from the conversion process. Turbine flowmeters, on the other hand, have been regarded as an industry standard because they are compact, rugged, reliable, and relatively inexpensive.

This paper describes the project objectives, the experimental installation, and the results of the comparison of the Coriolis and turbine type flowmeters in steady-state performance testing. Discussed are variations between the two types of flowmeters due to fuel characteristics, fuel handling equipment, acoustic and vibration interference and installation effects. Also included in this paper are estimations of measurement uncertainties for both types of flowmeters.

Results indicate that the agreement between Coriolis and turbine type flowmeters is good over the entire steady-state operating range of a typical gas turbine engine. In some cases the repeatability of the Coriolis flowmeter is better than the manufacturers specification. Even a significant variation in fuel density (10%), and viscosity (300%), did not appear to compromise the ability of the Coriolis flowmeter to match the performance of the turbine flowmeter.
The Influence of Load Distribution on Secondary Flow in Straight Turbine Cascades
Authors: Weiß Andreas P. , Fottner Leonhard
Published: February 2015

This paper describes an experimental study of the three-dimensional flow within two highly loaded turbine cascades subjected to the same overall load but different load distributions. Data were obtained using pneumatic probes, pressure tappings and a surface flow visualization technique. It is found that the general nature of the flow is similar for both cascades. In the exit plane the cascades show different spanwise loss distributions. However, the averaged secondary loss is quite similar in this plane. Examining the measurements further downstream and also by comparing the calculated mixed-out values it becomes clear that a higher magnitude of secondary loss is generated by the front-loaded cascade.
Numerical Simulations of Unsteady Cascade Flows
Authors: Dorney Daniel J. , Verdon Joseph M.
Published: February 2015

A time-accurate Navier-Stokes analysis is needed for understanding the relative importance of nonlinear and viscous effects on the unsteady flows associated with turbomachinery blade vibration and blade-row noise generation. For this purpose an existing multi-blade-row Navier-Stokes analysis has been modified and applied to predict unsteady flows excited by entropic, vortical, and acoustic disturbances through isolated, two-dimensional blade rows. In particular, time-accurate, nonreflecting inflow and outflow conditions have been implemented to allow specification of vortical, entropic, and acoustic excitations at the inlet, and acoustic excitations at the exit, of a cascade. To evaluate the nonlinear analysis, inviscid and viscous numerical simulations were performed for benchmark unsteady flows and the predicted results were compared with analytical and numerical results based on linearized inviscid flow theory. For small amplitude unsteady excitations, the unsteady pressure responses predicted with the nonlinear analysis show very good agreement, both in the field and along the blade surfaces, with linearized inviscid solutions. Based on a limited range of parametric studies, it was also found that the unsteady responses to inlet vortical and acoustic excitations are linear over a surprisingly wide range of excitation amplitudes, but acoustic excitations from downstream produce responses with significant nonlinear content.
A Linearized Euler Analysis of Unsteady Transonic Flows in Turbomachinery
Authors: Hall Kenneth C. , Clark William S. , Lorence Christopher B.
Published: February 2015

A computational method for efficiently predicting unsteady transonic flows in two- and three-dimensional cascades is presented. The unsteady flow is modelled using a linearized Euler analysis whereby the unsteady flow field is decomposed into a nonlinear mean flow plus a linear harmonically varying unsteady flow. The equations that govern the perturbation flow, the linearized Euler equations, are linear variable coefficient equations. For transonic flows containing shocks, shock capturing is used to model the shock impulse (the unsteady load due to the harmonic motion of the shock). A conservative Lax-Wendroff scheme is used to obtain a set of linearized finite volume equations that describe the harmonic small disturbance behavior of the flow. Conditions under which such a discretization will correctly predict the shock impulse are investigated. Computational results are presented that demonstrate the accuracy and efficiency of the present method as well as the essential role of unsteady shock impulse loads on the flutter stability of fans.
Detailed Flow Measurements in a Centrifugal Compressor Vaneless Diffuser
Authors: Pinarbasi Ali , Johnson Mark W.
Published: February 2015

Hot wire anemometer measurements have been made in the vaneless diffuser of a 1 metre diameter low speed backswept centrifugal compressor using a phase lock loop technique. Radial, tangential and axial velocity measurements have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wake flow pattern and the blade wakes. The passage wake is located on the shroud side of the diffuser and mixes out slowly as the flow moves through the diffuser. The blade wakes, on the other hand, distort and mix out rapidly in the diffuser. Contours of turbulent kinetic energy are also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced.
Periodicity and Repetivity of Unsteady Measurements of an Annular Turbine Cascade at Off Design Flow Conditions
Authors: Bölcs A. , Körbächer H.
Published: February 2015

A two-dimensional section of a gas turbine cascade has been investigated experimentally in an annular non-rotating cascade facility as regards to its steady-state and time-dependent aerodynamic characteristics at off-design flow conditions. The blades vibrated in the first traveling wave bending mode.

Steady-state and unsteady data were obtained for an off-design incidence angle of about 22° and for an isentropic outlet Mach number of M2s=1.19. At this flow condition, a separation bubble was present on the suction surface close to the leading edge. A shock appeared at trans- and supersonic outlet flow conditions on the suction surface. The data showed high unsteady loads close to the leading edge and in the shock region. It was found that the steady and the unsteady pressures in the shock region on the blade surface seemed to be very sensitive to small changes in the flow conditions.

The periodicity and repetitivity of the steady and the unsteady pressures (σ=180°) was checked at several circumferential channel positions. This was done to figure out to which extend test data obtained in an annular ring channel can serve as a basis for the comparison with numerically obtained data.

The aim of this paper is to show where problems may arise when comparing calculated results with test data.
Optimization of a Diffuser With Splitter by Numerical Simulation
Authors: Drtina P. , Dalbert P. , Rütti K. , Schachenmann A.
Published: February 2015

Three-dimensional, viscous, and compressible flow calculations have been performed in order to improve the performance of a radial compressor diffuser with splitter. All calculations were carried out applying a commercially available finite-volume Navier-Stokes code. Diffuser design procedure, grid generation and boundary conditions are described in detail. For each diffuser type several operating points ranging from the surge limit to choke were considered. Velocity distributions showing regions of separation are discussed for different diffuser geometries. The downstream evolution of the pressure recovery coefficient is given along both diffuser channels. Calculations have been verified by experimental investigations on full scale diffuser prototypes providing pressure values at defined locations.
Three-Dimensional Analysis of Turbine Rotor Flow Including Tip Clearance
Authors: Heider R. , Duboue J. M. , Petot B. , Billonnet G. , Couaillier V. , Liamis N.
Published: February 2015

A 3D Navier-Stokes investigation of a high pressure turbine rotor blade including tip clearance effects is presented.

The 3D Navier-Stokes code developed at ONERA solves the three-dimensional unsteady set of mass-averaged Navier-Stokes equations by the finite volume technique. A one step Lax-Wendroff type scheme is used in a rotating frame of reference. An implicit residual smoothing technique has been implemented, which accelerates the convergence towards the steady state. A mixing length model adapted to 3D configurations is used.

The turbine rotor flow is calculated at transonic operating conditions. The tip clearance effect is taken into account. The gap region is discretized using more than 55,000 points within a multi-domain approach.

The solution accounts for the relative motion of the blade and casing surfaces. The total mesh is composed of five sub-domains and counts 710,000 discretization points. The effect of the tip clearance on the main flow is demonstrated. The calculation results are compared to a 3D inviscid calculation, without tip clearance.
Prediction of Invsicid Flow in Axial Turbines in Comparison With Measurements
Authors: Haspel N. , Mayer J. F. , Stetter H.
Published: February 2015

A CFD code for simulation of 3D inviscid throughflow in turbine stages will be presented in this paper. The discretization is realized by a finite difference method applying a transformation procedure. The time dependent Enter equations are solved by the explicit time marching method of Lax, Wendroff and Richtmyer. The coupling between stator and rotor flow is achieved by circumferentially averaged flow data, enabling the simulation of low frequency flow fluctuations.

The flow through a gas turbine stator is simulated by the code. In this case secondary flow phenomena caused by a nonuniform inlet flow are of special interest. A throughflow calculation of the last stage of a LP steam turbine shows that the program is able to manage 3D complex transonic flows as well. The CFD results are compared in both cases with experimental data.
Effects of Variational Particle Restitution Characteristics on Turbomachinery Erosion
Authors: Hamed Awatef , Kuhn Timothy P.
Published: February 2015

This paper presents the results of an investigation to determine the effects of variational particle rebounding models on surface impacts and blade erosion patterns in gas turbines. The variance in the particle velocities after the surface impacts are modeled based on the experimental measurements using Laser Doppler Velocimetry (LDV) under varying flow conditions. The probabilistic particle trajectory computations simulate the experimental variance in the particle restitution characteristics using cumulative distribution functions and random sampling techniques. The results are presented for the particle dynamics through a gas turbine flow field and are compared to those obtained with deterministic rebound models based on experimental mean values.
An Optimum Balance Weight Search Algorithm
Authors: Austrow James C.
Published: February 2015

A mathematical description for an optimum balance weight search algorithm for single plane multipoint balance is presented. The algorithm uses influence coefficients, either measured or known beforehand, and measured complex vibration data to determine an optimum balance correction weight. The solution minimizes the maximum residual vibration. The algorithm allows user defined balance weights to be analyzed and evaluated. A test case is presented showing actual results and comparison with a least square solution algorithm. An efficient multiplane influence coefficient calculation scheme is also presented.
A Semianalytical Emission Model for Diffusion Flame, Rich/Lean, and Premixed Lean Combustors
Authors: Rizk N. K. , Mongia H. C.
Published: February 2015

To enhance gas turbine combustor performance and emissions characteristics better design methods need to be developed. In the present investigation, an emission model that simulates a detailed chemical kinetic scheme has been developed to provide the rate of reactions of the parent fuel, an intermediate hydrocarbon compound, CO, and H2. The intermediate fuel has variable carbon and hydrogen contents depending on operating conditions, that were selected in the development effort to simulate actual operation of rich/lean, diffusion flame, and lean combustor concepts. The developed reaction rate expressions address also the limited reaction rates that may occur in the near wall regions of the combustor due to the admittance of radial air jets and cooling air in these regions. The validation effort included the application of the developed model to a combustor simulated by a multiple-reactor arrangement. The results indicate the accurate duplication of the calculations obtained from the detailed kinetic scheme using the developed model. This illustrates the great potential of using such a unified approach to guide the design of various types of combustors to meet the more stringent emissions and performance requirements of next generation gas turbine engine.
Unsteady Aerodynamic Forcing Functions: A Comparison Between Linear Theory and Experiment
Authors: Feiereisen John M. , Montgomery Matthew D. , Fleeter Sanford
Published: February 2015

The unsteady flow field generated by rotating rows of perforated plates and airfoil cascades are mathematically split into vortical and potential components using two methods, one relying entirely on velocity data and the other utilizing both velocity and unsteady static pressure data. The propagation and decay of these split flow perturbations are then examined and compared to linear theory predictions. The perforated plate gusts closely resemble linear theory vortical gusts. Both splitting methods indicate that they are dominantly vortical gusts with insignificant unsteady static pressure perturbations. The airfoil gusts resemble linear theory combined vortical and potential gusts. The recombined airfoil gusts using the vortical and potential components calculated by the method using only unsteady velocity data do not necessarily resemble the measured gusts, nor do they behave axially as predicted by linear theory. The recombined airfoil gusts using the linear theory components calculated by the method using both unsteady velocity and unsteady static pressure data do resemble the measured gusts and behave axially as predicted by linear theory, with the vortical component propagating unattenuated and the potential component decaying at the rate predicted by linear theory.
Mashproekt Scientific and Production Association: A Designer of Gas Turbines for Marine and Industrial Applications
Authors: Romanov Victor I.
Published: February 2015

The first gas turbine unit for Navy application was developed in the Soviet Union in 1950s. It was installed as a boost power unit in a patrol boat and consisted of an aircraft engine rated at about 3000 kW, a free power turbine and a gear box. A successful experience of the unit application permitted to make a decision of establishing a designing organization and production works for marine gas turbine units development and manufacturing in Nikolayev. “Mashproekt” scientific and production association is currently developing technical documentation and prototype engines and units and “Zarya” production association is manufacturing engines in series production. It was planned to develop a gas turbine engine consisting of a two-spool coaxial compressor, a straight-flow combustion chamber, high pressure and low pressure turbines and a free power turbine. Such design meets more fully all-mode operation requirements for a marine propulsion unit. At first simple sycle engines were developed consisting of a gas turbine and a gear box which were used as boost units (CODAG configuration). A significant event was defined with the development of a gas turbine propulsion unit rated at 26 400 kW (13 200 × 2) which consisted of two engines combined through a common gear box (Twin Pac version) (Fig. 1).
Passive Control of Flow Induced Vibrations by Splitter Blades
Authors: Chiang Hsiao-Wei D. , Fleeter Sanford
Published: February 2015

Splitter blades as a passive control technique for flow induced vibrations is investigated by developing an unsteady aerodynamic model to predict the effect of incorporating splitter blades into the design of an axial flow blade row operating in an incompressible flow field. The splitter blades, positioned circumferentially in the flow passage between two principal blades, introduce aerodynamic and/or combined aerodynamic-structural detuning into the rotor. The unsteady aerodynamic gust response and resulting oscillating cascade unsteady aerodynamics, including steady loading effects, are determined by developing a complete first-order unsteady aerodynamic analysis together with an unsteady aerodynamic influence coefficient technique. The torsion mode flow induced vibrational response of both uniformly spaced tuned rotors and detuned rotors are then predicted by incorporating the unsteady aerodynamic influence coefficients into a single-degree-of-freedom aeroelastic model. This model is then utilized to demonstrate that incorporating splitters into axial flow rotor designs is beneficial with regard to flow induced vibrations.
A Method for the Calculation of the Tip Clearance Flow Effects in Axial Flow Compressors: Part I — Description of Basic Models
Authors: Nikolos I. K. , Douvikas D. I. , Papailiou K. D.
Published: February 2015

Theoretical models for the investigation of the phenomena connected with the tip clearance are presented. The mass flow rate through the gap, the formation and evolution of the leakage vortex and the losses occurring inside and downstream of the gap are considered.

Firstly, a model was developed for the description of the flow through the gap, which uses different simple velocity profiles at the gap exit. The model recognizes the basic flow characteristics inside the gap.

A new method is proposed for the calculation of the shed vorticity and the formation of the leakage vortex. The moment of momentum equation is used along with the conservation of mass, in order to provide the circulation of the leakage vortex.

A diffusion model for the vorticity distribution is used for the calculation of the pressure deficit field, so that the total pressure losses due to the presence of the leakage vortex, are derived. Theoretical results are compared to experimental ones for compressor and turbine cascades as well as for single rotors. The agreement between theory and experiment is good.
Expansion of USN Gas Turbine Repair Into the Intermediate Level Repair Facility
Authors: Hartranft John J.
Published: February 2015

The USN gas turbine maintenance philosophy over the years has migrated from an “Upkeep by Exchange” philosophy to one that takes extensive advantage of engine modularity and the ability to repair it inplace to reduce life cycle support costs. This expansion of repair has taken place at the “Intermediate Level” of maintenance. It involves both internal engine repair aboard ship and module repair in the Intermediate Level maintenance facility. This takes maximum advantage of an aero gas turbine’s small, lightweight, internally accessible and modular design.

This new direction in maintenance has been driven mainly by the extensive size of the surface Navy’s gas turbine fleet and its projected repair costs. The end result has been an increase in engine availability and a minimal escalation in removals and repair and support costs as the fleet continues to expand and age. What has been learned is that cost savings are achievable when operator level, Intermediate Level and depot level maintenance are molded together with engineering to form a unified maintenance approach vice treating each of these as separate and distinct, noncommunicative entities.
Simulation of Space Solar CBC Power Systems
Authors: Diao Zheng-Gang
Published: February 2015

The paper describes a computer program to simulate space solar closed Brayton cycle (CBC) power systems. The program has been written for IBM-compatible microcomputers. Either analytical equations or performance characteristics of individual components are used to model the steady-state operation of the power system. The results obtained by calculation have been compared with ground test data.
Analysis of Kalina Cycle Designs With Modifications Including a Distillation Column
Authors: Glasare Karin B. , Olsson Eva K. , von Spakovsky Michael R. , Svedberg Gunnar
Published: February 2015

It has been shown in a number of studies that the Kalina cycle can have considerably higher efficiencies than the Rankine cycle. An especially advantageous application is as a bottoming cycle to a gas turbine. In this paper a gas turbine topping cycle has been assumed.

Three different configurations of the Kalina bottoming cycle have been examined and compared. One is an original cycle (El-Sayed and Tribus, 1985) with a flash separator. In another configuration, a second feedwater heater is added and in a third a distillation column instead of a flash separator is used. The stages of the column are heated by exchanging heat with two different streams in the Kalina distillation condensation subsystem.

For each configuration, the different compositions in the cycle have been varied. The First Law efficiency and the exergetic efficiency have been calculated as well as the rate of exergy loss in each unit. The results show that the cases with the best performance of each of the three configurations differ very little in efficiency. The original cycle has the highest efficiency for the conditions studied.
Development of ASTM Standards in Support of Advanced Ceramics Development: A Status Report
Authors: Brinkman Charles R. , Quinn George D. , McClung Robert W.
Published: February 2015

The ASTM Committee C-28 on Advanced Ceramics was organized in 1986 when it became apparent that ceramics were being considered for extensive use in such applications as heat engines in the automotive and aerospace industries. It was determined that these standards should be written for the production, inspection, testing, data analysis, and probabilistic design for utilization of advanced ceramics (where advanced ceramics include both monolithic and composite materials). The ASTM Committee C-28 is organized into five subcommittees as follows: Properties and Performance, Design and Evaluation, Characterization and Processing, Ceramic Composites, and Nomenclature. A summary overview is given of work performed to date (1992) and ongoing efforts in developing standards by these various subcommittees.
Restoration of Thinned Airfoils by Application of Physical Vapor Deposition Coating
Authors: Rose Daniel P. , Price George D. , Saenz Joe A. , Lawton Paul F.
Published: February 2015

The GTCP331-200/250 auxiliary power unit (APU) is used to provide electrical power and compressed air for commercial aircraft, including the Boeing 757 and 767, and Airbus A310. The turbine section of this engine is a three stage axial flow configuration. Due to the combined effect of oxidation and erosion, the useful life of the first stage turbine blade may be limited by loss of material on the airfoil. The effect of material loss is reduction of the airfoil thickness and chord length.

This paper discusses a repair that restores the airfoil dimensions by buildup with a physical vapor deposition coating. The repair process includes incoming dimensional inspection of the airfoil, physical vapor deposition with tapered thickness to restore airfoil dimensions, and post deposition processing. The evaluation includes airfoil dimensional inspection, metallographic verification of coating integrity, and finite element modeling to illustrate the effect of material buildup on different locations of the airfoil.
Gas Turbine Operating in Combined and Regenerative Cycles Using Liquid Metal Heat Exchangers
Authors: Perkavec M. A.
Published: February 2015

Liquid metal technology for heat transfer was developed for use in nuclear power stations. Applied to a gas turbine regenerative cycle plant, it makes high heat exchange rates in the regenerator, and low pressure losses as well on the air side as on the exhaust side economically possible. Its application permits combined cycle as well as regenerative cycle operation of the same gas turbine. Mixed operation in any ratio is also easily accomplished, so that the ratio of heat and electricity produced by the gas turbine plant is variable within a wide range.

This paper presents the results of thermodynamic calculations for such plants and describes the optimization of design parameters. Influences of the individual parameters of the regenerative cycle on the power output and efficiency of the plant are examined, and the reasonable limits for this application are outlined.

The advantages of applying liquid metal technology to gas turbines, such as a virtually pressureless liquid metal system, flexible operation, and separate optimization of the heat exchange coefficients for the air and exhaust flows are discussed.

Reference is also made to emissions, which are more complicated than those for combined or regenerative cycles because the plant is operated in both modes.
Starting System Upgrade for General Electric Frame 5 Gas Turbine Generators
Authors: Skladony Robert M. , Hendry Morgan L.
Published: February 2015

Most gas turbine generators rely on a mechanical starting system to accelerate the gas turbine generator from zero to some intermediate speed to enable gas turbine ignition and then provide torque assistance to a higher speed until the gas turbine is self-sustaining. In the past, both automatic and non-automatic methods of disconnecting the starting system from the turbine have been used. This paper presents the reasons for and details of the retrofit of automatic synchronous self-shifting clutches into existing starting systems of General Electric MS-5001 gas turbine generator sets at Consolidated Edison Company, Brooklyn, New York.
Rig Tests of Two-Zone Combustor of Stationary GT Unit
Authors: Tumanovsky A. G. , Sokolov K. Y. , Gutnik M. N. , Sudarev A. V. , Zaharov Y. I. , Winogradov E. D. , Akulov V. A.
Published: February 2015

The results of experimental investigation of basic parameters of full-scale two-zone fire-tube of the combustor for the modern gas turbine unit. Specifics of fuel burnup, formation of pollutants in both microflame and premixed combustion using double zone design are presented. Dependences of combustor characteristics and optimized algorithm of combustor loading are illustrated.
Effect of Acoustic Resonance Condition on Wake Generated Rotor Blade Gust Response
Authors: Manwaring Steven R. , Fleeter Sanford
Published: February 2015

Unsteady aerodynamic blade row response is generally categorized as either subresonant or superresonant, with an acoustic resonance at the points where these regions meet. Although these far field acoustic responses are critical to obtaining correct predictions from linearized unsteady flow models, they are a subject of some controversy, both analytically and experimentally. In this paper, multistage axial flow compressor acoustic resonance conditions, including both subresonant and superresonant unsteady aerodynamic response in the immediate vicinity of an acoustic resonance, are experimentally investigated. This is accomplished by quantifying these acoustic resonance and subresonant and superresonant blade row interaction phenomena in terms of their effect on the rotor blade row periodic unsteady pressure response. The subresonant and superresonant acoustic environments are established by changing the number of vanes while maintaining the number of rotor blades, thereby altering the unsteady stator-rotor interactions and the interblade phase angle and by varying the Mach number without changing the blade row interactions. First the first stage rotor row periodic unsteady pressure response to a downstream stator-rotor interaction generated acoustic wave is studied. Then, the gust unsteady aerodynamic response of the first stage rotor row due to IGV wakes, with the IGV-instrumented first stage rotor itself configured to generate subresonant and superresonant conditions is considered. Appropriate data are correlated with predictions.
Toward Modeling the Concurrent Design of Aircraft Engine Turbines
Authors: Lee Hauhua , Goel Sanjay , Tong Siu S. , Gregory Brent , Hunter Scott
Published: February 2015

This paper describes our approach and experiences in constructing the Turbine Auto–Designer (TAD), an automated concurrent design system for aircraft engine turbines. In TAD, the design process is modeled based on the computer programs of a representative design system. It integrates three domains of the manual design process: preliminary design, detailed aerodynamic design, and detailed mechanical design.

The manual design of turbines is an iterative redesign process involving the use of many sets of Computer Aided–Engineering (CAE) programs. The entire design process is modeled at four levels: analysis, automation, optimization, and concurrency. TAD is implemented with Engineous, a generic software shell for engineering design. Parts of TAD are already in use in day–to–day design practice for low–pressure turbines. In many cases of preliminary design, TAD can obtain better results quicker than the optimum obtained manually. Results also show that, for detailed aerodynamic analysis, the system can reduce the cycle time from days to hours.
High Temperature Coatings for Protection Against Turbine Deterioration
Authors: Tabakoff W. , Metwally M. , Hamed A.
Published: February 2015

In this research, an investigation was conducted to study the fly ash particles associated with the erosion behavior of alloys and coatings which are widely used in gas and steam turbines. The erosion behavior of many alloys and protective coatings has been investigated experimentally at high temperatures using a specially designed wind erosion tunnel. The erosion results show the effect of velocity, temperature and the impact angle on the erosion rate.
Experimental Study of the Effects of Bleed Holes on Heat Transfer and Pressure Drop in Trapezoidal Passages With Tapered Turbulators
Authors: Taslim M. E. , Li T. , Spring S. D.
Published: February 2015

Trailing edge cooling cavities in modern gas turbine blades often have trapezoidal cross-sectional areas of relatively low aspect ratio. To enhance cooling effectiveness in these passages, they are roughened with tapered turbulators. Furthermore, to provide additional cooling for the trailing edge, the cooling air may be ejected through trailing edge slots as it moves radially along the cooling passage. The tapered turbulators, in conjunction with the presence of these slots along the smaller base of the trapezoidal cavity, create spanwise as well as longitudinal variations in heat transfer coefficient on the turbulated walls. Moreover, the continuous variation of cooling air velocity along these passages causes a continuous change in static pressure which also requires investigation. Liquid crystals are used in this experimental investigation to study the effects of tapered turbulators on heat transfer coefficients in trailing edge passages with and without bleed holes. The tapered turbulators are configured on two opposite walls of the trapezoidal test section in a staggered arrangement with an angle of attack to the mainstream flow, α, of 90°. Nine different test geometries consisting of two passage aspect ratios, AR, were tested over a range of turbulator aspect ratios, ARt, blockage ratios, emax/Dh, pitch-to-height ratios, S/emax, and Reynolds numbers. Channel pressure losses were also measured and both heat transfer and friction factor results for several geometries are compared. It is concluded that a) there exists a large spanwise variation in heat transfer coefficient in test sections with no bleed holes, b) adding bleed holes to the smaller base of the trapezoidal cavity gives a spanwise velocity component to the mainstream flow and reduces this variation, and c) Nusselt numbers measured in the test sections with bleed holes correlate well with local Reynolds number.
A Thermal Fatigue Model for Probabilistic Lifetime Strength of Propulsion System Components
Authors: Boyce L. , Bast C. C.
Published: February 2015

This paper describes the development of methodology for a probabilistic material strength degradation model, that provides for quantification of uncertainty in the lifetime material strength of structural components of aerospace propulsion systems subjected to a number of diverse random effects. The model has most recently been extended to include thermal fatigue. The discussion of thermal fatigue, in the context of probabilistic material strength degradation, is the central feature of this paper. The methodology, for all effects, is embodied in two computer programs, PROMISS and PROMISC. These programs form a “material resistance” model that may be used in the aerospace structural reliability program, NESSUS or in other applications. A probabilistic material strength degradation model for thermal fatigue and other relevant effects, in the form of a postulated randomized multifactor interaction equation, is used to quantify lifetime material strength. Each multiplicative term in the model has the property that if the current value of an effect equals the ultimate value, then the lifetime strength will be zero. Also, if the current value of an effect equals the reference value, the term equals one and lifetime strength is not affected by that particular effect. Presently, the model includes up to four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep and thermal fatigue. Statistical analysis of experimental data for Inconel 718 obtained from the open literature and laboratory reports is also included in the paper. The statistical analysis provided regression parameters for use as the model’s empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep and thermal fatigue. Finally, using the PROMISS computer program, a sensitivity study was performed with the calibrated random model to illustrate the effects of mechanical fatigue, creep and thermal fatigue, at about 1000 °F, upon random lifetime strength.
PG5361 Steam Injected Cogeneration Plant
Authors: Wen Xueyou , Wei Yingxin , Zou Jiguo
Published: February 2015

This paper gives a short description of the first-in-China steam-injected gas turbine plant for use in power stations. The adoption of steam injection techniques can lead to a significant enhancement in power output and sizable reduction in oil consumption rate.
Numerical Prediction of Profile and Endwall Losses for Multi-Splitter Turbine Cascades
Authors: Zhou D. M. , Zhang Z. G. , Li Y. S.
Published: February 2015

A simple numerical method for predicting the profile loss and the endwall secondary loss of multi-splitter turbine cascade in subsonic flow is presented. A variational finite element potential flow solver is used to obtain the main flow through the blade passages, the loss due to the surface friction is calculated using an integral boundary layer method, the trailing-edge loss is calculated directly from the empirical correlation, and a semi-empirical model for estimating the endwall secondary loss is also provided. The rationality of the approach is justified by the agreement of the prediction with a range of experimental measurement.
Simulation of Diffuser Flow Using an Euler Solver With a Distributed Loss Model
Authors: Krückels J. , Mayer J. F. , Stetter H.
Published: February 2015

The flow inside a diffuser which serves as outlet of the last turbine stage is strongly influenced by the tip leakage jet of the last blade row.

For the computation of diffuser flow a quasi 3D Euler solver with a simple model for the approximation of viscous effects was developed. A body force which is calculated as a function of velocity gradients normal to the streamwise direction is included in the Euler equations. Computational cost for calculations using this method remains low, permitting its use as a design tool for turbine diffusers.

Comparison of numerical results with experimental data for an annular axial radial diffuser at the outlet of a steam turbine model is presented. Flowfields for different tip clearances show a strong dependence of the pressure recovery on the tip leakage jet. Numerical results agree well with measurements.
Modal Analysis and Forced Response of Coupled Mistuned Cyclic Systems: A Singular Perturbation Approach
Authors: Happawan G. S. , Bajaj A. K. , Nwokah O. D. I.
Published: February 2015

The effect of small deterministic parameter perturbations on the forced response of nearly periodic structures with cyclic symmetry has been investigated. The general theory developed herein is applicable to any nth order strongly coupled cyclic system with two arbitrary and independent variations in system parameters that destroy the cyclic symmetry. The specific system studied may be regarded as a simplified model of a strongly coupled bladed-disk assembly. Singular perturbation methods along with modal expansion analysis are applied to gain a physical insight into the effects of perturbations on the eigenvalues, the eigenvectors as well as the forced response amplitudes. The study shows that, under appropriate conditions, the splitting and veering of eigenvalues due to mistunings or small parameter variations increases the amplitude of vibration of some blades quite significantly than would be predicted on the basis of an analysis of the perfectly tuned system. Further, the modal bifurcations lead to uneven vibration amplitudes irrespective of the stiffness of the coupling springs. The variation in blade amplitudes are also found to be strongly dependent on the type of engine order excitation for the same set of mistuning parameter.
Status of Low NOx Combustor Development
Authors: Solt J. Charles , Tuzson John
Published: February 2015

Stationary gas turbine development is experiencing exceptional growth. This growth is driven by the great demand for large industrial turbines in electric power generation and by progressively more severe environmental regulations. The momentary status of developments is described here with special emphasis on emerging NOx reduction options.
An Advanced Method of Processing Liquid Crystal Video Signals From Transient Heat Transfer Experiments
Authors: Wang Zuolan , Ireland Peter T. , Jones Terry V.
Published: February 2015

A new method of processing the liquid crystal colour change data obtained from transient heat transfer experiments is presented. The approach uses the full intensity history recorded during an experiment to obtain an accurate measurement of the surface heat transfer coefficient at selected pixels. Results are presented for a model of a turbine blade cooling passage with combined ribs and film cooling holes. The implementation of the technique and the advantages to be gained from its application are discussed.
Exploring How Shroud Constraint Can Affect Vibratory Response in Turbomachinery
Authors: Yang M.-T. , Griffin J. H.
Published: February 2015

Unusual resonant responses were observed during spin pit tests of shrouded blades. The unusual behavior consisted of blades that exhibited strong response over a broad range of frequencies. The frequencies of peak response were considerably lower than predicted and were also lower than those observed in other tests of nominally identical wheels. In addition, the tracking plots of blade amplitudes versus frequency were truncated rather than displaying the usual sharp peaks seen in other tests. The unusual response is potentially dangerous since high vibratory response could be excited over a broad range of operating speeds.

The blades were designed to be free standing with gaps of approximately 10 milli-inches between neighboring shrouds. It is hypothesized that shroud contact at the blade tips could cause the unusual vibratory response. A simple model of a blade with shroud contact is developed in order to determine if shroud contact could cause blades to vibrate in the observed manner. The model is unusual in that it seeks to explore how contact could cause the blade to respond at lower (rather than higher) frequencies since contact typically increases the constraints on a structure and raises its natural frequencies.
Coatings for the Protection of Turbine Blades From Erosion
Authors: Walsh P. N. , Quets J. M. , Tucker R. C.
Published: February 2015

Many types of turbines, including aircraft gas turbines, steam turbines, and power recovery turbines, suffer from solid particle erosion caused by a variety of materials ingested into the machines. Utilization of various laboratory erosion tests tailored to the specific application by using various erodents, temperatures, velocities, and angles of impact, have been shown to be effective in the development and selection of coatings for the erosion protection of turbine blades and other components. Detonation gun coatings have demonstrated their efficacy in providing substantial protection in many situations. It has now been shown that several tungsten carbide and chromium carbide Super D-Gun™ coatings not only have better erosion resistance than their D-Gun analogs, but cause little or no degradation of the fatigue properties of the blade alloys. Nonetheless, caution should be employed in the application of any laboratory data to a specific situation and additional testing done as warranted by the turbine designer.
Correlation Between Microstructure and Mechanical Properties of Diffusion Brazed MAR-M 247
Authors: Miglietti W.
Published: February 2015

Diffusion brazing is a joining process utilized in the manufacture and repair of turbine blades and vanes. MAR-M247 is an investment cast Ni-based superalloy used for turbine blading and has good strength properties at high temperatures. The objectives of this work was to develop a diffusion brazing procedure to achieve high strength joints. A commercially available diffusion brazing filler metal of composition Ni-15Cr-3,5B of 100 μm thickness was used. With the desire to eliminate brittle centre-line phases, the effects of the processing variables (only temperature and time) on the joint microstructure was studied. Once the metallurgy of the joint was understood, mechanical property assessments were undertaken i.e. tensile and creep rupture tests, and the latter being the severest test to evaluate joint strength. The results demonstrated that the diffusion brazed joints had nearly equivalent mechanical strength to that of the parent metal. This showed that the resultant diffusion brazing parameters enabled effective and reliable joining of MAR-M247.
Effects of Leaning and Curving of Blades With High Turning Angles on the Aerodynamic Characteristics of Turbine Rectangular Cascades
Authors: Han Wanjin , Tan Chunqing , Shi Hong , Zhou Mochun , Wang Zhongqi
Published: February 2015

To intensively understand the effects of the origination and development of centralized vortices on the aerodynamic characteristics of turbine rectangular cascades with high turning angles, an experiments with 5-hole micro spherical probes, accompanied by color helium bubble flow display, were carried out. The measurement planes are arranged as 3 before, 6 in and 1 after, the cascade. The experiments reveal that the origination and development of horseshoe vortices and passage vortices as well as the interaction of the latters almost dominate the whole flow field of traditional linear cascades. Lean linear cascades favor the horseshoe vortices and passage vortices in the acute angle zone, and impede those in the obtuse angle zone. So it is a logical result to adopt the negatively curved blades, whose pressure surfaces and both endwalls compose both obtuse angles respectively, to improve the cascade aerodynamic characteristics.
Calibrating Ultrasonic Images for the NDE of Structural Materials
Authors: Gilmore Robert S. , Glaeser Andreas M. , Wade Janet C.
Published: February 2015

Ultrasonic imaging is taking a larger and larger role in the NDE of turbine engine materials and in support of fracture mechanics calculations. It is also playing an increasing role in quality and process control. For most fracture toughness calculations, it is necessary to establish the accuracy with which a flaw’s size and shape are imaged, whether single or multiple flaws are involved, and the spacing of multiple flaws. Because of these requirements, resolution has become an issue as well as detection sensitivity. There are a number of resolution targets that can provide this type of calibration information for an ultrasonic imaging system. A fused quartz USAF 1951 target, similar to the patterns used in this work, was first used by Gilmore (1986), but Gilmore’s pattern was superficial and subsurface evaluations were limited to focusing on the pattern from the opposite side of the blank and monitoring the reflection from what is now the target backwall. Work by Peyton (1977) did produce buried targets in titanium samples, but there was no practical method to produce buried targets in high-temperature ceramics until the techniques developed by Rodel and Glaeser (1987) were used to produce the targets described in this paper.

Optically transparent resolution targets make it feasible to visually verify that the resolution target has been correctly fabricated. An image of the target with a candidate ultrasonic transducer then permits quantitative image resolution estimates to be made even when the interrogating acoustic beam contains significant refractive aberration. This is important because useful subsurface images can be acquired with the use of acoustic beams that are aberrated to the point that diffraction-limited beamwidth calculations are meaningless.

This work also demonstrates how the interdisciplinary skills of manufacturing companies can be combined with those of universities to produce results that any one of the individual members of the team could not have produced alone, without significant increases in labor, time, and cost.