bluuebunny/crossref_metadata_2025 huggingface dataset:
An Application of Octant Analysis to Turbulent and Transitional Flow Data
Authors: Volino Ralph J. , Simon Terrence W.
Published: February 2015

A technique called “octant analysis” was used to examine the eddy structure of turbulent and transitional heated boundary layers on flat and curved surfaces. The intent was to identify important physical processes that play a role in boundary layer transition on flat and concave surfaces. Octant processing involves the partitioning of flow signals into octants based on the instantaneous signs of the fluctuating temperature, t′; streamwise velocity, u′; and cross-stream velocity, v′. Each octant is associated with a particular eddy motion. For example, u′<0, v′>0, t′>0 is associated with an ejection or “burst” of warm fluid away from a heated wall. Within each octant, the contribution to various quantities of interest (such as the turbulent shear stress, −u′v′, or the turbulent heat flux, v′t′) can be computed. By comparing and contrasting the relative contributions from each octant, the importance of particular types of motion can be determined. If the data within each octant is further segregated based on the magnitudes of the fluctuating components so that minor events are eliminated, the relative importance of particular types of motion to the events that are important can also be discussed. In fully-developed, turbulent boundary layers along flat plates, trends previously reported in the literature were confirmed. A fundamental difference was observed in the octant distribution between the transitional and fully-turbulent boundary layers, however, showing incomplete mixing and a lesser importance of small scales in the transitional boundary layer. Such observations were true on both flat and concave walls. The differences are attributed to incomplete development of the turbulent kinetic energy cascade in transitional flows. The findings have potential application to modelling, suggesting the utility of incorporating multiple length scales in transition models.
Calculation of Heat Transfer to Turbine Blading Using Two-Dimensional Boundary Layer Methods
Authors: Harasgama S. P. , Tarada F. H. , Baumann R. , Crawford M. E. , Neelakantan S.
Published: February 2015

The calculation of the external boundary layer and associated heat transfer to turbine blading is described. Three separate Two-Dimensional Boundary Layer programs were utilised in this study. The programs incorporated the k-epsilon turbulence model with several different formulations. The test case chosen for this study was the von Karman Institute blade VKI Tech. Note-174, Sept-1990.

It is shown that in most cases all programs tend to predict the correct behaviour of the onset of transition. However, the transition length between the laminar and turbulent values is predicted too abruptly on the blade suction side. It was found that the magnitude of the predicted heat transfer coefficient was most consistent with experimental values for exit Mach numbers between 0.7–0.9, and for all inlet turbulence levels and Reynolds numbers. For higher blade exit Mach numbers in the transonic region (M > 0.95) it was difficult to correctly predict the heat transfer in comparison with experimental data. The predicted values were all higher than the measurement. For this blade, the pressure side is quite well predicted for most of the operating conditions.
Three Dimensional Time-Marching Inviscid and Viscous Solutions for Unsteady Flows Around Vibrating Blades
Authors: He L. , Denton J. D.
Published: February 2015

A 3-dimensional non-linear time-marching method of solving the thin-layer Navier-Stokes equations in a simplified form has been developed for blade flutter calculations. The discretization of the equations is made using the cell-vertex finite volume scheme in space and the 4-stage Runge-Kutta scheme in time. Calculations are carried out in a single-blade-passage domain and the phase-shifted periodic condition is implemented by using the shape correction method. The 3-D unsteady Euler solution is obtained at conditions of zero viscosity, and is validated against a well-established 3-D semi-analytical method. For viscous solutions, the time-step limitation on the explicit temporal discretization scheme is effectively relaxed by using a time-consistent two-grid time-marching technique. A transonic rotor blade passage flow (with tip-leakage) is calculated using the present 3-D unsteady viscous solution method. Calculated steady flow results agree well with the corresponding experiment and with other calculations. Calculated unsteady loadings due to oscillations of the rotor blades reveal some notable 3-D viscous flow features. The feasibility of solving the simplified thin-layer Navier-Stokes solver for oscillating blade flows at practical conditions is demonstrated.
Reduction in Secondary Flows and Losses in a Turbine Cascade by Upstream Boundary Layer Blowing
Authors: Biesinger Thomas E. , Gregory-Smith David G.
Published: February 2015

The effect of upstream tangential blowing on the secondary flows has been studied in a turbine cascade of rotor blades. The aim is to reduce the secondary flows and losses, but in the evaluation an accounting procedure for the energy for blowing is required. The experimental results show that the effect of the increasing blowing is first to thicken the inlet boundary layer, giving greater secondary flow and more loss, and then as re-energisation of the inlet boundary layer takes place together with increasing counter streamwise vorticity, the passage vortex is progressively weakened, with a corresponding reduction in loss. Low rather than high angle blowing is shown to be more effective as the jet is kept closer to the end wall, and strong similarities could be obtained with the flow patterns from previous work with a skewed inlet boundary layer. However when the energy for inlet blowing is included, no net gain is achieved due mainly to the mixing loss of the injected air. Overall gains may be achievable, if combined with such features as injection for film cooling.
Optimal Design of Split Ring Dampers for Gas Turbine Engines
Authors: Niemotka Michael A. , Ziegert John C.
Published: February 2015

Vibration analysis techniques used for labyrinth air seals are presented, along with a derivation of the methods used to calculate the dissipation capability of split ring dampers. After defining the problem in classical optimization format, the methods used to automate the process are presented, along with the results for a particular test case. For the case considered, the optimal designs were found to lie at or near the design space boundaries.
Use of CFD Methods to Design Engine Nacelles
Authors: Joubert H. , Goutines M.
Published: February 2015

The challenge for current and future nacelles of commercial engines is to obtain: -low transonic drag in cruise condition, -low weight and reduced dimensions without reducing the low speed operating domain (maximum incidence, crosswind, etc) and low noise level. This paper explains how various designs can be improved by using modern numerical methods.

Concerning air inlets, 3D Euler code and boundary layer code are used for prediction of divergence Mach number and drag in cruise conditions. Low speed behaviour is also obtained for various flight conditions which cause high local incidences on air inlet sections. Attention is mainly focused on attached flow limits. CFD method calibrations based on existing tests results are needed for that work.

Bypass and core nozzle design use axisymmetric Navier-Stokes calculations for the prediction of thrust and flow coefficients relative values. This calculation also helps on development of adequate designs of the throat region and provides detailed analysis of the core nozzle flowfield including interaction of outer cold jet.

These methods are applied to the design of an advanced nacelle for a high bypass ratio engine. This nacelle is equiped with an original core cowl doors thrust reverser. Consequently the nacelle length and weight have been significantly reduced.

The main numerical results obtained on this nacelle are presented including some results for the installation of this nacelle under a wing.
Three-Dimensional Vibration Analysis of Rotating Laminated Composite Blades
Authors: McGee O. G. , Chu H. R.
Published: February 2015

This work offers the first known three-dimensional (3-D) continuum vibration analysis for rotating, laminated composite blades. A cornerstone of this work is that the dynamical energies of the rotating blade are derived from a 3-D elasticity-based, truncated quadrangular pyramid model incorporating laminated orthotropicity, full geometric nonlinearity using an updated Lagrangian formulation and Coriolis acceleration terms. These analysis sophistications are included to accommodate the nonclassical directions of modern blade designs comprising thin, wide chord lifting surfaces of laminated composite construction. The Ritz method is used to minimize the dynamical energies with displacements approximated by mathematically complete polynomials satisfying the vanishing displacement conditions at the blade root section exactly. Several tables and graphs are presented which describe numerical convergence studies showing the validity of the assumed displacement polynomials used herein. Nondimensional frequency data is presented for various rotating, truncated quadrangular pyramids, serving as first approximations of practical blades employed in aircraft engines and fans. A wide scope of results explain the influence of a number of parameters coined to rotating, laminated composite blade dynamics, namely aspect ratio (a/b), chord ratio (c/b), thickness ratio (b/h), variable thickness distribution (hl/ht), blade pretwist angle (ϕo), composite fiber orientation angle (θ), and angular velocity (Ω). Additional examples are given which elucidate the significance of the linear and nonlinear kinematics used in the present 3-D formulation along with the importance of the Coriolis acceleration terms included in the analysis.
Unsteady Wake Over a Linear Turbine Blade Cascade With Air and CO2 Film Injection: Part II — Effect on Film Effectiveness and Heat Transfer Distributions
Authors: Mehendale Anant B. , Han Je-Chin , Ou Shichuan , Lee C. Pang
Published: February 2015

The effect of unsteady wake flow and air (D.R.=0.97) or CO2 (D.R.=1.48) film injection on blade film effectiveness and heat transfer distributions was experimentally determined. A spoked wheel type wake generator produced the unsteady wake. Experiments were performed on a five airfoil linear cascade in a low speed wind tunnel at the chord Reynolds number of 3×105 for the no wake case and at the wake Strouhal numbers of 0.1 and 0.3. A model turbine blade with several rows of film holes on its leading edge, and pressure and suction surfaces (−0.2<X/C<0.4) was used. Results show that the blowing ratios of 1.2 and 0.8 provide the best film effectiveness over most of the blade surface for CO2 and air injections, respectively. An increase in the wake Strouhal number causes a decrease in film effectiveness over most of the blade surface for both density ratio injectants and at all blowing ratios. On the pressure surface, CO2 injection provides higher film effectiveness than air injection at the blowing ratio of 1.2; however, this trend is reversed at the blowing ratio of 0.8. On the suction surface, CO2 injection provides higher film effectiveness than air injection at the blowing ratio of 1.2; however, this trend is reversed at the blowing ratio of 0.4. CO2 injection provides lower heat loads than air injection at the blowing ratio of 1.2; however, this trend is reversed at the blowing ratio of 0.4. Heat load ratios under unsteady wake conditions are lower than the no wake case. For an actual gas turbine blade, since the blowing ratios can be greater than 1.2 and the density ratios can be up to 2.0, hence, a higher density ratio coolant may provide lower heat load ratios under unsteady wake conditions.
Investigation on Suppression of the Dynamic Distortion of 2-D Diffuser
Authors: Wang Shuo , Huang Xijun
Published: February 2015

Three passive control methods of dynamic total pressure distortion have been developed in a 2–D diffuser in this paper: a fore–positioned shock stabilizing rod on a porous plate (model Q), a mid–positioned shock stabilizing rod on a porous plate (model Z), a porous plate (model K) and the original model without any control.

From the experiment results, we observe that the PCSB (Passive Control of Shock wave / Boundary layer) technique used in the diffuser is effective to decrease the dynamic distortion. We conclude that:

a) Different flow regions and their characteristic frequencies in the diffuser have been found.

b) The interaction between the terminal shock wave and the boundary layer produces the peak value of the dynamic distortion.

c) The steady total pressure varies inversely with the dynamic components of the total pressure along the height at the exit of the diffuser.

d) The effects of different positions of the shock stabilizing rod on the dynamic distortion are relative to the upstream total pressure of the diffuser.

e) New explanation about the production of the distortion has been given.
Thermal Tip Clearance Control for Centrifugal Compressor of an APU Engine
Authors: Eisenlohr G. , Chladek H.
Published: February 2015

To master todays demand for efficiency and compactness of centrifugal compressor components for small gasturbine engines the main attention must not only be given to the aerodynamic design of the impeller and diffuser components, but also to the installation situation of the surrounding parts. A vital aspect is the tip clearance control between impeller and shroud casing over the total operating range.

Using the radial compressor for a small gasturbine engine, developed at BMW Rolls-Royce, the importance of tip clearence control is demonstrated. The possibilities for influencing and optimizing passive tip clearance control by design features are described; transient expansion processes must be considered when using a thermal tip clearance control.

The results of the design calculations are compared with the results on the teststand and the engine itself. An effort is made to find a qualitative influence of tip clearance to the engine power output at operating conditions. This qualitative description is substantiated by test results with different tip clearances at the compressor teststand.
Large Eddy Simulation of Bluff Body Stabilised Turbulent Premixed Flames
Authors: Rydén Roland , Eriksson Lars-Erik , Olovsson Stefan
Published: February 2015

Flow calculations for a premixed flame behind a bluff body flame holder using a conventional finite difference code with a standard k-ε turbulence model have been found to give poor predictions of the overall flow field. A major factor is believed to be the inadequately modelled large scale turbulence in the wake region. In order to improve the numerical prediction capability a large eddy simulation (LES) technique, which has recently given very good predictions for the non-reacting flow around the same flame holder, has been extended to handle reacting flow. This paper presents a combustion model which considers the influence of turbulence on the effective chemical reaction rates and which is adapted to the LES framework. The combustion model is of the “eddy dissipation type” previously developed by Magnussen.

The present flow simulation code has been applied on the premixed bluff body flow case and results are compared with measurement data from gas analysis, LDA (Laser Doppler Anemometry) and CARS techniques. Significant improvements in the overall predictions are demonstrated even on a coarse mesh.
Computational Modeling of an Aircraft Engine Combustor to Achieve Target Exit Temperature Profiles
Authors: Lawson R. J.
Published: February 2015

A GE high bypass turbofan aircraft engine combustor has been successfully modeled in an effort to define liner cooling and dilution modifications necessary to create inboard peaked and flat exit temperature profiles. A fully elliptic three–dimensional body–fitted computational fluid dynamics code (CONCERT3D) was used to solve for the flow field variables. The modeling results provided detailed flow information that was used to define cooling and dilution modifications. Boundary condition flow levels for the model were derived from COBRA, a one–dimensional pressure driven flow distribution program. The complex inlet boundary conditions defining the combustor inlet swirl cup discharge flow were generated via a detailed CONCERT2D model.

A baseline model was first created and tuned to match existing test results. Using the tuned model, dilution and cooling patterns were varied to analytically achieve the two desired temperature profiles. Approximately ten attempts were needed to match both target profiles. The derived changes were then applied to actual combustor hardware and new exit temperature profiles were measured in full component rig tests. Both tested configurations closely matched the target profiles on the first attempt, greatly reducing the number of hardware modifications and tests typically needed to fulfill profile requirements.
Turbulence Structure of Flow in a Porous Tube With Annular Outer Flow
Authors: Ramamoorthy Sundar , Khodabakhsh Fariborz , Munukutla Sastry
Published: February 2015

Turbulence measurements were conducted inside a porous-wall tube insert placed coaxially in a solid-wall outer tube. The outer tube diameter was 8 inches. The diameter of the inner tube was 6.5 inches. Three different porosities of 7.5, 15 and 22.5 percent were used for the inner tube. The average velocity of the flow in the outer tube was 55 ft/sec. The nominal Reynolds Number, based on diameter and mean velocity of the flow in the outer tube, is 2 × 105. Results are presented for the three rms fluctuations, the Reynolds stress and the turbulence kinetic energy. The nature of the turbulence activity was examined by using the quadrant splitting scheme.
Pollutant Emissions From Gas Fired Turbine Engines in Offshore Practice: Measurements and Scaling
Authors: Røkke N. A. , Hustad J. E. , Berg S.
Published: February 2015

Field measurements of CO, NOx, N2O and UHC from natural gas fired gas turbines have been performed at oil production platforms in the North Sea and at an oil and gas processing plant on-shore. The measuring objects comprised a total of 17 engines. The emissions were measured at different loads, ranging from idle to 100% power output.

The emissions vary considerably as a function of load. NOx and UHC agree reasonably well with manufacturers’ data. The NO2/NOx ratio is inversely proportional to the load. The CO emissions are somewhat lower than specified. N2O emissions are typically less than 2 ppmv @15% O2, dry.

From the collected data, a scaling law for NOx emissions is developed. The scaling law is based on machine specific parameters governing NOx production and will apply to gas-fired turbine engines at various loads in the power range and makes indicated. Good agreement between measured and predicted NOx emissions from the proposed correlation is achieved.
A Single System for 2D and 3D Airfoil Analysis
Authors: Jennings Richard M.
Published: February 2015

New, independent dimensional analysis systems compare measured section data as well as full 3D airfoil data to corresponding solid models to identify dimensional errors in individual parts and to highlight probable sources of error in manufacturing processes.

Graphic display of the results speeds analysis of airfoils, complete blades, integrally bladed rotors (IBRs), disks, disk slots, and engine “plumbing.”
Numerical Predictions of Idle Power Emissions From Gas Turbine Combustors
Authors: Valachovic Timothy G.
Published: February 2015

Numerical analyses of two existing gas turbine combustors gave predictions of idle power emissions. The calculated exit emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO) are compared to engine test data. For the first combustor, the effects of varying fuel flow on the UHC and CO emissions were investigated while liner cooling flow changes were examined in the second combustor. A fully elliptic three-dimensional computational fluid dynamics code based on pressure correction techniques was employed to model the flow field inside the combustor. Fuel injection was handled using a Lagrangian liquid droplet spray model coupled to the gas phase equations. The combustion model consists of a two-step global reaction mechanism with reaction rates computed using a modified eddy-breakup technique. The numerical algorithm employs non-orthogonal curvilinear coordinates and the standard k-e turbulence model. The results for the first combustor agree well with the test measurements. The baseline result for the second combustor shows good agreement with test data. Predicted effects of cooling flow changes agree with trends from past experience of idle power emissions.
Humid Air Gas Turbine Cycle: A Possible Optimization
Authors: Stecco S. S. , Desideri U. , Bettagli N.
Published: February 2015

The humid air turbine (HAT), patented by Fluor Daniel, is an innovative cycle which allows to obtain an increase in efficiency and power production. The modification proposed by DEF allows to optimise the plant when natural gas is injected in the combustion chamber.

Assuming a TIT (Temperature Inlet Turbine) at 1273 K and the cooling of recirculating water in the refrigerators, we studied the effects of the relative humidity and the compression ratio on the cycle’s performances.

The aim of this paper is to suggest the parameters which allow to obtain high efficiency with high specific power, the possibility to modulate power production without a decrease in efficiency and low water consumption.
Design and Performance Evaluation of a CBC Solar Space Power System: The Influence of Orbital and Solar Conditions
Authors: Massardo Aristide F.
Published: February 2015

Design and performance evaluation of solar space Closed Brayton Cycle (CBC) is described in this paper taking into account the influence of orbital and solar conditions.

With fixed external conditions (insolation, Tsink, power) overall performance and area of the plant are obtained and optimized (plant area minimization), while to evaluate plant mass a detailed and complete design of the plant components is carried out.

Utilizing as the input the results obtained with fixed external conditions, plant transient orbital analysis (TOA) is performed taking into account modification of insolation, Tsink, and power to be generated versus orbit time, (quasi steady transient analysis).

All these methods have been fully integrated — the common inputs are interchanged and the output of one code is directly input to the other codes — in a complete design procedure, named CBC-SPACE, suited for Low Earth Orbit (LEO) station power plant design.

The most important results are presented and discussed, while the importance of this study is pointed out taking also into account the possibility to extend this analysis to SDCC (solar dynamic combined cycle) plant proposed by the author (Massardo, 1991).
Numerical Simulation of an Annular Combustor
Authors: Di Martino P. , Cinque G.
Published: February 2015

A numerical model to solve three-dimensional turbulent reactive flows in arbitrary shapes is presented. The conservative form of the primitive-variable formulation of steady density-weighted Navier Stokes equations written for a general curvilinear system is adopted.

Turbulent transport is described by the k-ε model. The reactions associated with heat release are assumed sufficiently fast for chemical equilibrium to prevail on an instantaneous basis and the influence of local turbulent fluctuations in mixture strenght accounted for by a β-probability density function.

The numerical scheme is based on a non-staggered grid (cartesian velocity components and pressure located at the same grid-points) and a special interpolation technique is used to avoid checkerboard oscillations.

The present model was used to simulate an annular combustion chamber for which experimental results were available. The agreement between calculation and experiments ranges from fair to good.
Shock Loss Attenuation in Transonic Rotors Using Area Ruling Concepts for Part-Span Dampers
Authors: Roberts William B. , Sandercock Donald M.
Published: February 2015

The transonic area rule as proposed by R. T. Whitcomb (1952) has been successfully applied to external flow since that time. This paper reports a preliminary semi-empirical study done in the early 1980’s to determine if a specific area ruling concept can be applied to internal flows, in particular to transonic fans using part-span dampers (i.e., part-span shrouds). Cascade and rotor correlations reported herein indicate that the area rule may be applied to internal flows. A simple precursory channel flow experiment has been done that shows an attenuation of shock losses using area ruling in supercritical internal flow.
Base-Metal Thermocouple Technology for Improved Temperature Measurement in Gas Turbine Engines
Authors: Furniss C. Paul
Published: February 2015

During the next decade there will be growing pressures placed upon the manufacturers of gas turbines to produce more operationally efficient engines.

There are two main end-use groupings for gas turbines. The parameters for efficiency may prove to be quite different for these end-use groups, requiring a separate emphasis for engineering design.

With respect to aircraft propulsion gas turbines, the efficiencies may tend towards greater fuel economy and unit power outputs. In contrast to this the ground based gas turbine units may require increased unit power output but be restricted by the tightening emission requirements being dictated by international pollution laws.

One of the key areas of focus for engineering design, in order to satisfy such performance demands, is that of improved operational control of the turbine.

The process variables requiring accurate, reliable and repeatable monitoring and control include rotational speed, linear speed, pressure, mass flow rate and temperature. Whilst all of these phenomena require correct control, it may be argued that temperature is of extreme importance for both an operational efficiency and safety viewpoint.

This paper will attempt to explore the problems associated with conventional methods of gas turbine temperature measurement and discuss possible solutions using novel new technologies that will allow the earlier realisation of these efficiency goals.
Unsteady Wake Over a Linear Turbine Blade Cascade With Air and CO2 Film Injection: Part I — Effect on Heat Transfer Coefficients
Authors: Ou Shichuan , Han Je-Chin , Mehendale Anant B. , Lee C. Pang
Published: February 2015

The effect of unsteady wake flow and air (D.R.=1.0) or CO2 (D.R.=1.52) film injection on blade heat transfer coefficients was experimentally determined. A spoked wheel type wake generator produced the unsteady wake. Experiments were performed on a five airfoil linear cascade in a low speed wind tunnel at the chord Reynolds number of 3×105 for the no wake case and at the wake Strouhal numbers of 0.1 and 0.3. Results from a blade with three rows of film holes in the leading edge region and two rows each on the pressure and suction surfaces show that the Nusselt numbers are much higher than those for the blade without film holes. On a large portion of the blade, the Nusselt numbers ‘without wake but with film injection’ are much higher than for ‘with wake but no film holes’. An increase in wake Strouhal number causes an increase in pressure surface Nusselt numbers; but the increases reduce at higher blowing ratios. As blowing ratio increases, the Nusselt numbers for both density ratio injectants (air and CO2) increase over the entire blade except for the transition region where the effect is reversed. Higher density injectant (CO2) produces lower Nusselt numbers on the pressure surface, but the numbers for air and CO2 injections are very close on the suction surface except for the transition region where the numbers for CO2 injection are higher. From this study, one may conclude that the additional increases in Nusselt numbers due to unsteady wake, blowing ratio, and density ratio are only secondary when compared to the dramatic increases in Nusselt numbers only due to film injection over the no film holes case.
Measurement of Surface Temperature Using a Laser-Induced Fluorescence Thermal Imaging System
Authors: Chyu M. K. , Bizzak D. J.
Published: February 2015

This paper describes a novel, non-intrusive thermal imaging system based on the fluorescence properties of an europium-doped lanthanum oxysulfide (Eu+3:La2O2S) thermographic phosphor. In this system the phosphor coating on a test surface is excited by a pulsed Nd:YAG laser. The resulting fluorescent emission of the temperature-sensitive 512 nm transition, along with that of the relatively temperature independent 620 nm transition, is acquired using an image-intensified charged coupled device (ICCD) camera. The ratio of the 512- and 620-nm emissions, integrated over a set gating period, is then correlated with temperature. Quality data obtained from a calibration procedure have demonstrated that the present approach can be more advantageous than many existing thermal imaging techniques. The system has been specifically designed to provide two-dimensional temperature measurements with high accuracy and exceptional spatial resolution. Because of the extremely short fluorescent lifetimes of various thermographic phosphors (∼μs), applicability of the technique to fast-moving or rotating surfaces is very promising.
Heat Pipe Cooling of Turboshaft Engines
Authors: Anderson William G. , Hoff Sandra , Winstanley Dave , Phillips John , DelPorte Scott
Published: February 2015

Reduction in turbine engine cooling flows is required to meet the IHPTET Phase II engine performance levels. Heat pipes, which are devices with very high thermal conductance, can help reduce the required cooling air. A survey was conducted to identify potential applications for heat pipes in turboshaft engines. The applications for heat pipe cooling of turbine engine components included the power turbine first stage vanes, shroud, and case, the HP turbine vanes and shroud, and the T5 temperature probe. Other potential applications for heat pipe cooling include regenerative cycle and intercooling, bearing cooling, IR signature reduction, and active clearance control. Calculated performance benefits included an increase in specific shaft horsepower, and a decrease in specific fuel consumption, as determined with an IHPTET Phase II turboshaft engine performance model. For example, using heat pipes to cool the power turbine vanes, shroud, and case would increase the specific shaft horsepower by 6 percent, while decreasing the specific fuel consumption by 2.2 percent. While this study examined turboshaft engines, most of the applications are also applicable to turbofan engines.
The Use of the ALON™ Process to Prevent Corrosion in the Cheng Cycle Cogeneration Plant
Authors: McGill William A.
Published: February 2015

A cogeneration plant produces two forms of energy using a single source. Today, the term typically describes a system which generates (1) electricity through the use of the gas turbine and (2) steam. Both the output of the gas turbine and the generation of steam depend upon a single source of heat.
Turbo Expanders for Power Generation State of the Art and Design Optimization: Pipeline Pressure Regulating Stations
Authors: Cleveland Anthony
Published: February 2015

In these environmentally sensitive times we are bombarded with exhortations to “reduce, re-use, recycle and replace” almost everything we consume including our limited resources of non renewable energy. Conservation is a key word in this so-called new technology but in reality many of these measures of reducing consumption of valuable resources were being practiced years ago in more difficult times, i.e., wartime.
Performance Criteria for Gas Turbine Cogeneration Plant
Authors: Sarabchi K. , Khoshravan E.
Published: February 2015

With current gas turbine practice up to two-thirds of the energy available in the fuel is lost in the form of unused heat, By making practical use of this waste heat in a recovery boiler to produce steam for district heating or process applications it is possible to reduce the energy wastage to as little as 10 percent.

In this paper different performance criteria for assessment of a gas turbine cogeneration plant (GTCP) have been defined and compared with each other, Also, the practical range of performance criteria have been determined.
Numerical Investigations on the Effects of Swirling Combustor Exit Flow on HP-Turbine Inlet Flow for the Industrial Gas Turbine THM 1304
Authors: Bauermeister K. J. , Dohmen H.-J. , Simon H.
Published: February 2015

To reduce gas turbine exhaust emissions the combustion system of the MAN GHH industrial gas turbine THM 1304 (ISO power 9250 kW) has been modified. The two outboard combustors in a V–configuration enabled to enlarge the chambers and thus to increase the retention time. Compared to the initial design the nature of combustor exit flow is considerably changed to an additional swirling flow.

To estimate the effects of these flow conditions on gas turbine performance the flow towards the high pressure turbine should be investigated. For that purpose a numerical flow simulation in the casing between the combustion chambers and the high pressure turbine nozzles has been accomplished. A Navier–Stokes–Solver (Finite Element Method) has been applied to the computation of the threedimensional turbulent flow.

The essential results, especially the flow conditions in front of the HP–turbine nozzles are presented with respect to the idealized combustor exit flow conditions. Besides the swirl strength, the direction of rotation and the swirl relation are varied. It is shown, that the flow at HP–turbine inlet is essentially characterized by the mainly centripetally directed combustor exit flow. Dependent on the above mentioned swirl flow parameters the characteristic flow distribution at HP–turbine inlet changes more or less. In the most favourable case the mass flow distribution at HP–turbine inlet varies circumferentially approx. ±14% and in the worst case approx. ±26%. Associated deviations from the ideal axial flow direction of approx. ±30° respectively ±40° are calculated.
Coupled Blade Bending and Torsional Shaft Vibration in Turbomachinery
Authors: Schaber U. , Mayer J. F. , Stetter H.
Published: February 2015

The forced vibration of turbomachinery blading induced by torsional vibration of the rotor shaft is investigated. Torsional shaft vibrations, caused for example by disturbances in the electrical network, jeopardize the long blades in low pressure stages of steam and gas turbine generator rotors. A simple finite element model consisting of beam elements is used to calculate free and forced vibration. A parameter study has been performed to show the influence of design parameters like mass relation and eigenfrequency relation of the uncoupled system parts. The vibration analysis of a large steam turbine generator rotor is presented.
Processing of a Single Crystal Casting for Heavy-Duty Gas Turbine Blades: Creep and Metal/Mould Reaction Behavior of Al2O3-SiO2 Shell Mould
Authors: Iijima K. , Yoshinari A. , Ishida T. , Yasuda T. , Matsuzaki H. , Shimomura K.
Published: February 2015

Al2O3-SiO2 moulds have been adopted successfully as shell moulds for a single crystal casting for jet engine blades. Heavy-duty gas turbine blades also have large dimensions and complex features comparable to those of jet engines. Then shell moulds should be subjected to similar severe service conditions when casting heavy-duty gas turbine blades. Creep behavior of 90mol%Al2O3+10mol%SiO2, which was manufactured through the lost wax process by using fused Al2O3 powder (average particle size, 15 μ m), was studied at temperatures of 1450 to 1550 °C. in four-point bending creep tests. Creep deflection rates were linearly proportional to stresses. The proposed creep mechanism was Al grain boundary diffusion at the interfacial regions between Al2O3 stucco powder. No severe metal/mould reaction appeared for the region adjacent to the interface between moulds and Ni base superalloys.
S1A-02 STIG Gas Turbine Test Rig
Authors: Wen Xueyou , Jin Jierong , Fu Zheng , Zou Jiguo
Published: February 2015

This paper presents a brief account of the first Chinese experimental plant of a steam-injected gas turbine and its various systems. Also given in the paper are its main design features and test results.
A Novel Method for Refurbishing Used Hot Section Gas Turbine Blades
Authors: Kempster Adrian , Czech Norbert
Published: February 2015

During the normal operation of a land based gas turbine attack will occur of the gas washed surfaces of the rotating and stationary blades in the turbine hot section. This attack and its intensity can be variable depending on the blades position in the turbine hot section. This attack will progressively degrade these gas washed surfaces even if these surfaces have been previously coated with a protective layer. During the service period of the turbine, it will be necessary to refurbish the blades from the hotter section of the turbine. One of the refurbishment steps will be to provide the blades with a suitable replacement coating to afford protection until the next service period.

Conventional refurbishment techniques used to clean the blade surface rely on abrasive cleaning and/or chemical pickling. These processes may be capable of removing superficial oxidation and any residual coating but are not able to consistently remove the substrate material that has suffered from corrosive attack. It is important that this attacked substrate layer is removed completely otherwise any residual corrosion products, particularly the presence of deeply penetrated sulphides in grain boundaries, could significantly reduce the life of any subsequent coating.

The technique described in this Paper essentially activates the surface layer of the substrate that is corroded, thus rendering it more easily removed by chemical and physical means. It is possible by this method to remove up to 400 microns of the substrate material and provided that all the corrosion products are contained within this zone, it is demonstrated how this produces a clean unattacked surface that is necessary for any subsequent welding, brazing or recoating operation.
Flow Physics Leading to System Instability in a Centrifugal Pump
Authors: Wo Andrew M. , Bons Jeffrey P.
Published: February 2015

The off-design performance in a centrifugal pump is investigated experimentally. The objective is to identify flow features which lead to the onset of surge as the fundamental pumping system instability. Results show that there are primarily two reasons for the onset of surge as the flow is reduced in the pump studied: (a) adverse flow in the tongue region and (b) destabilizing effect of the pipe diffuser. The former is due to premature diffusion of the flow entering the tongue region, which is manifested by increased flow recirculation through the tongue/impeller gap and flow separation on the volute outer side-wall opposite the tongue. These effects in the tongue region flow coupled with the destabilizing behavior of the pipe diffuser lead to the eventual unstable pump operation.
The Operational Stability of a Centrifugal Compressor and its Dependence on the Characteristics of the Subcomponents
Authors: Hunziker René , Gyarmathy Georg
Published: February 2015

A centrifugal compressor was tested with three different diffusers with circular-arc vanes. The vane inlet angle was varied from 15° to 30°. Detailed static wall pressure measurements show that the pressure field in the diffuser inlet is very sensitive to flow rate. The stability limit regularly occurred at the flow rate giving the maximum pressure rise for the overall stage. Mild surge arises as a dynamic instability of the compression system. The analysis of the pressure rise characteristic of each individual subcomponent (impeller, diffuser inlet, diffuser channel,…) reveals their contribution to the overall pressure rise. The diffuser channels play an inherent destabilizing role while the impeller and the diffuser inlet are typically stabilizing. The stability limit was mainly determined by a change in the characteristic of the diffuser inlet. Further, the stability limit was found to be independent of the development of inducer-tip recirculation.
Rotating Stall Acoustic Signature in a Low Speed Centrifugal Compressor: Part 1 — Vaneless Diffuser
Authors: Lawless Patrick B. , Fleeter Sanford
Published: February 2015

An experimental study is performed to identify spatially coherent pressure waves which would serve as precursors to the development of an instability in the Purdue Low Speed Centrifugal Research Compressor when configured with a vaneless diffuser. To achieve this, sensitive electret microphones were uniformly distributed around the circumference in the inlet and diffuser sections of the compressor. Fourier analysis of simultaneously sampled data from these microphone arrays was employed to identify the development of dominant spatial modes in the pressure field in the compressor. The transition to stall was observed to be a gradual process, with the growth of the pressure waves into those corresponding to a large-scale stall condition occurring over a time span of twenty-six impeller revolutions. The excitation of the pressure waves, as indicated by spatial Fourier analysis, occurred 14 impeller revolutions before small changes were evident in the microphone signals, and 26 revolutions before the stall condition could be considered fully developed.
Effect of Permeable Ribs on Heat Transfer and Friction in a Rectangular Channel
Authors: Hwang Jenn-Jiang , Liou Tong-Miin
Published: February 2015

Heat transfer and friction characteristics in a rectangular channel with perforated ribs arranged in–line on two opposite walls are investigated experimentally. Five perforated rib open–area–ratios (0, 10%, 22%, 38%, and 44%) and three rib pitch–to–height ratios (10, 15, and 20) are examined. The Reynolds number ranges from 5000 to 50000. The rib height–to–channel hydraulic diameter ratio and the channel aspect ratio are 0.081 and 4, respectively. Laser holographic interferometry is employed not only to measure the heat transfer coefficients of the ribbed wall but also to determine the rib apparent permeability. It is found that ribs with appropriately high open–area–ratio and high Reynolds number are permeable, and the critical Reynolds number for evidence of flow permeability decreases with increasing the rib open–area–ratio. Results of local heat transfer coefficients further show that the permeable ribs have an advantage of obviate the possibility of the hot–spots. Moreover, the duct with permeable ribs gives a higher thermal performance than that with solid–type ribs.
Tip Leakage Flow in Linear Compressor Cascade
Authors: Kang S. , Hirsch C.
Published: February 2015

Tip leakage flow in a linear compressor cascade of NACA 65-1810 profiles is investigated, for tip clearance levels of 1.0, 2.0 and 3.25 percent of chord at design and off-design flow conditions. Data, velocity and pressures, are collected from three transverse sections inside tip clearance and sixteen sections within flow passage. Tip separation vortex influence is identified from the data. Leakage flow mixing is clearly present inside the clearance and has a significant influence on the internal loss.
Development of a Transonic Front Stage of an Axial Flow Compressor for Industrial Gas Turbines
Authors: Katoh Y. , Kashiwabara Y. , Ishii H. , Tsuda Y. , Yanagida M.
Published: February 2015

This paper describes the aerodynamic blade design of a highly-loaded three-stage compressor, which is a model compressor for the front stage of an industrial gas turbine.

Test results are presented that confirm design performance. Some surge and rotating stall measurement results are also discussed.

The first stator blade in this test compressor operates in the high subsonic range at the inlet. To reduce the pressure loss due to blade surface shock waves, a shock-free airfoil is designed to replace the first stator blade in an NACA-65 airfoil in a three-stage compressor. Comparison of the performance of both blades shows that the shock-free airfoil blade reduces pressure loss.

This paper also presents some experimental results for MCA (multi-circular arc) airfoils, which are used for first rotor blades.
An Investigation of Boundary Layer Development in a Multistage LP Turbine
Authors: Hodson H. P. , Huntsman I. , Steele A. B.
Published: February 2015

This paper describes an investigation of the behaviour of suction surface boundary layers in a modern multistage Low Pressure turbine. An array of eighteen surface-mounted hot-film anemometers was mounted on a stator blade of the third stage of a 4-stage machine. Data were obtained at Reynolds numbers between 0.9 × 105 and 1.8 × 105.

At the majority of the test conditions, wakes from upstream rotors periodically initiated transition at about 40% surface length. In between these events, laminar separation occurred at about 75% surface length. Because the wake-affected part of the flow appeared to be only intermittently turbulent, laminar separation also occurred at about 75% surface length while this flow was instantaneously laminar. At all but the lowest Reynolds numbers, the time-mean boundary layer appeared to have re-attached by the trailing edge even though it was not fully turbulent. It is inferred that the effect of the wakes on the performance of the bladerow is limited and that steady flow design methods should provide an adequate assessment of LP turbine performance during design.
Dynamic Forces From Single Gland Labyrinth Seals: Part II — Upstream Coupling
Authors: Millsaps Knox T. , Martinez-Sanchez Manuel
Published: February 2015

The standard lumped parameter model for flow in an eccentrically offset labyrinth seal, which assumes constant upstream and downstream boundary conditions, has been extended to include the effects of a non-uniform upstream cavity flow due to coupling. This new model predicts that the upstream perturbations in pressure and azimuthal velocity caused by this coupling, can have a very strong impact on the pressure distribution in the seal gland itself. Augmentation by a factor of four, over the uniform inlet model, is predicted under some circumstances. Although no precise comparison to the experimental data with this new model was possible, due to the lack of control over the face seal venting the upstream cavity to the center hub plenum, the calculated effect of this coupling was shown to be approximately what was required to restore quantitative agreement between the data and theory. The new theory can explain the anomalously large pressure non-uniformity previously found by other authors in short seals as well as the first few glands of multi-cavity seals.
Contribution of Thermal Radiation to the Temperature Profile of Ceramic Composite Materials
Authors: Tremante Andrés , Malpica Freddy
Published: February 2015

The steady energy transfer equation by simultaneous conduction and radiation in an absorbing, emitting and non-scattering gray planar medium is studied theoretically. For extremely high-temperature applications, where radiative transfer plays an important role, ceramic-matrix composites, considered as semitransparent materials, are being explored for potential use in turbine and compressors components, spacecraft structures, engine control systems and nuclear reactors. Exact solution of the above mentioned radiative problems is seldom possible and large-time consuming numerical approximations are then used. A technique combining an accurate physical formulation, the two-flux model, coupled to a fast numerical procedure for the calculation of the temperature and heat fluxes is described.