bluuebunny/crossref_metadata_2025 huggingface dataset:
A Blade by Blade Tip Clearance Measurement System for Gas Turbine Applications
Authors: Sheard A. G. , Killeen B.
Published: February 2015

It is difficult to make a reliable measurement of running clearance in the hostile environment over the blading of a modern gas turbine. When engine manufacturers require the measurement to be made over every blade during live engine tests, system reliability, ruggedness and ease of operation are of primary importance.

This paper describes a tip clearance measurement system that can measure clearance over every blade around a rotor. The measurement system concept is presented, and the system design described in detail. Commissioning of the measurement system on a compressor test facility, and the results obtained are discussed. An analysis of system performance during the commissioning trials concludes the paper.
Experimental and Numerical Study of Three-Dimensional Flows in a Mixed-Flow Pump Stage
Authors: Takemura T. , Goto A.
Published: February 2015

Internal flows of a low specific speed pump stage, having a mixed-flow impeller and a vaned bowl diffuser combination, have been investigated experimentally and numerically. Air was used as the test fluid, and the internal flows were measured at various locations and under various capacities. Flow calculations were made, for both the isolated impeller case and the complete stage case, using Denton viscous codes LOSS3D and MULTSTAGE14, by which the three-dimensional steady flow through multiple blade rows can be calculated using the inter-row mixing process. Experimental results showed the effects of the interaction between the impeller and the reverse flow, originating in the downstream diffuser, even at the design point capacity. While an impeller exit reverse flow occurred at the shroud side in the isolated impeller calculation, it was observed at the hub side in the complete stage case, showing good agreement with the experimental results. Although the flow in the diffuser was highly distorted due to a strong swirl flow, patterns of total pressure distribution could be well predicted by the complete stage calculation.
Laser Velocimeter Measurements in the Pump of an Automotive Torque Converter: Part II — Unsteady Measurements
Authors: Brun K. , Flack R. D. , Gruver J. K.
Published: February 2015

The unsteady velocity field found in the pump of an automotive torque converter was measured using laser velocimetry. Velocities in the inlet, mid-, and exit planes of the pump were investigated at two significantly different operating conditions: turbine/pump rotational speed ratios of 0.065, and 0.800. A data organization method was developed to visualize the three dimensional, periodic unsteady velocity field in the rotating frame. For this method, the acquired data is assumed to be periodic at synchronous and blade interaction frequencies. Two shaft encoders were employed to obtain the instantaneous angular position of the torque converter pump and turbine at the instant of laser velocimeter data acquisition. By proper “registration” of the data visualizing the transient interaction effects between the stator and the pump, and the pump and the turbine was possible. Results showed strong cyclic velocity fluctuations in the pump inlet plane as a function of the relative stator-pump position. Typical percent periodic fluctuations in the through flow velocity were 70% of the average through flow velocity. The upstream propagation influence of the turbine on the pump exit plane flow field was seen to he smaller. Percent periodic fluctuations of the through flow velocity were typically 30%. The effect of the stator and turbine on the mid-plane flow field was seen to be negligible. The incidence angle at the pump inlet fluctuated by 27° and 14° for the 0.065 and 0.800 speed ratios, respectively. Typical slip factors at the exit were 0.965 and fluctuated by less than 1%.
Comparison Between EBW and GTAW for TURMO IV C Compressor Blade Repairs
Authors: Miglietti W.
Published: February 2015

A research study was undertaken to evaluate whether electron beam welding (EBW) or gas tungsten arc welding (GTAW) could be utilised for repairs to the leading edges of the Turmo IV C compressor blades. These blades are manufactured from Ti-6Al-4V. The study entailed performing a series of welding trials. For the GTAW process a matching filler metal to the parent metal was used whereas for the EBW process, the welds were made autogenously. After metallographic examination of the weld microstructure, mechanical property assessments were undertaken, namely tensile and fatigue tests, the latter being a stringent test to evaluate the performance of the welded joint. The results demonstrated that the EB welds had equivalent properties to the parent metal whereas the GTA welds had poorer fatigue properties due to undesirable microstructure that resulted in the weld zone. The results achieved herein showed that the EBW process would be an appropriate technique for the restoration of these compressor blades.
Modelling and Control of HSFDs for Active Control of Rotor-Bearing Systems
Authors: El-Shafel A. , Hathout J. P.
Published: February 2015

This paper summarizes the development of hybrid squeeze film dampen (HSFDs) for active control of rotor vibrations. Previously, it was shown both theoretically and experimentally that HSFDs can be used for controlling rotor vibrations (El-Shafei, 1993). This is done by controlling the flow in a squeeze film damper through movable end seals, thus achieving the ability to change the damper from a short damper to a long damper and vice versa. However, the control of the HSFD was manual. In this paper, an automatically controlled circuit is developed for the HSFD, incorporating a pressure control servovalve for controlling the pressure in the scaling chambers. A complete mathematical model of this open-loop system is developed and is implemented on a digital computer. The transient behavior of the system, including the sealing ring dynamics, illustrates that the open-loop system exhibits well behaved, stable, and fast response. In addition it is shown that the HSFD can achieve any amount of damping between the short and long damper modes through the accurate positioning of the sealing rings. The simulation results illustrate that the automatically controlled HSFD can be a very useful device for the active control of rotors. A closed loop control strategy with feedback on rotor speed is also investigated both from the points of view of steady state and transient behaviors. It is shown that this closed loop strategy results in a much improved behavior of the rotor system.
Heat Transfer in an Air-Cooled Rotor-Stator System
Authors: Chen Jian-Xin , Gan Xiaopeng , Owen J. Michael
Published: February 2015

This paper describes a combined experimental and computational study of the heat transfer from an electrically-heated disc rotating close to an unheated stator. A radial outflow of cooling air was used to remove heat from the disc, and local Nusselt numbers were measured, using fluxmeters at seven radial locations, for nondimensional flow rates up to C = 9680 and rotational Reynolds numbers up to Reφ = 1.2 × 106. Computations were carried out using an elliptic solver with a low-Reynolds-number k-ε turbulence model, and the agreement between the measured and computed velocities and Nusselt numbers was mainly good.
Sensor Error Compensation in Engine Performance Diagnostics
Authors: Volponi Allan J.
Published: February 2015

The pursuit of reliable engine performance methods is as old as the gas turbine itself. Contemporary methods of engine fault isolation and assessment have centered around the use of modem estimation algorithms similar in nature to the Kalman filter and its derivatives. Those who are familar with such programs will offer the following quip, (apparently known to many but attributed to none), that the Kalman filter works well when you already know the answer, in other words, when the a-priori estimates are sufficiently close to the true values such as to produce small measurement residuals. Unfortunately, the ubiquity of measurement error ensures that this is generally not the case. A pivotal requirement for successful diagnostics becomes the ability to detect and assess the measurement error existing in raw engine data in an effort to mitigate its effect on potential engine fault mis-interpretation. The purpose of this paper is to outline the mathematical basis for the techniques in present use and to offer a generalization to a large measurement error compensation method which has been utilized effectively for over a decade.
Analysis of Transonic Turbomachinery Flows Using a 2-D Explicit Low-Reynolds k-ε Navier-Stokes Solver
Authors: Dejean F. , Vassilopoulos C. , Slmandirakis G. , Giannakoglou K. C. , Papailiou K. D.
Published: February 2015

An explicit, time-marching fractional-step solver for the calculation of the two-dimensional compressible Navier-Stokes equations is presented. The advantage of using a fractional-step analysis is its simplicity and the fact that greater time-steps are allowed, since the stability criterion is less strict compared to other explicit solvers. Turbulence is modeled through a low-Reynolds k-ε model, for which a novel artificial viscosity scheme is implemented, ensuring a smooth ε-distribution close to solid walls. The method is used in order to numerically investigate the flow field in three different cascades, namely a highly loaded transonic linear turbine guide vane cascade in six different flow conditions, a transonic steam turbine cascade in two different flow conditions and a low supersonic compressor cascade. Calculations are performed using both H- and C-type grids.
Disk/Cavity Wall Cooling Effectiveness Experiments With Air and CO2 as Coolants
Authors: Johnson B. V. , Daniels W. A.
Published: February 2015

Experiments were conducted with a turbopump drive disk/cavity model to determine the effects of coolant density on the composition of the fluid within a disk cavity. The 3-D, large-scale model simulated the aft cavity of the Space Shuttle Main Engine (SSME) high-pressure-fuel turbopump including the flow through the blade shanks of the second stage turbine and the nuts and bolts on the rotor and cavity walls. Coolant was injected near the bore of the turbine disk and gas sampling measurements were made to determine the fraction of the gas from each fluid source. Air was used as the gas entering the cavity through the blade shanks and air or carbon dioxide (CO2) was used as the coolant injected axisymetrically near the rotor bore. CO2 was also used as a trace gas when air was used as the simulated coolant. All the flow exited the cavity through the rim seal. CO2 concentration measurements were made to deterime the composition of gas withdrawn through pressure taps at selected radii from the disk bore to the simulated airfoil platforms. Results were obtained and are presented for a range of coolant flow rates. When air was used as coolant, the rotor wall concentrations were approximately 100 percent coolant from the disk bore to radii where momentum integral models indicate all the coolant is entrained in the disk boundary layers. When the coolant was CO2, having a density of approximately 1.5 times that of air, the coolant concentrations were generally less on both the rotor and cavity walls, indicating that the higher density coolant produced increased mixing with the upstream flow, entering near the cavity OD through the blade shanks.
Lyapunov’s Stability of Non-Linear Misaligned Journal Bearings
Authors: Nikoiakopouios Padelis G. , Papadopouios Chris A.
Published: February 2015

In this paper the stability of non-linear misaligned rotor-bearing systems is investigated, using the Lyapunov direct method. A finite element formulation is used to determine the journal bearing pressure distribution. Then the linear and nonlinear stiffness, damping and hybrid (depended on both displacements and velocity) coefficients are calculated A general method of analysis based on Lyapunov’s stability criteria is used to investigate the stability of non-linear misaligned rotor bearing systems. The equations of motion of the rigid rotor on the non-linear bearings are used to find a Lyapunov function using some of the above coefficients, which are depending on L/D ratio and the misalignment angles ψa, ψr. The analytical conditions for the stability or instability of some examined cases are given and some examples for the orbital stability are also demonstrated.
A New Endwall Model for Axial Compressor Throughflow Calculations
Authors: Dunham John
Published: February 2015

It is well recognised that the endwall regions of a compressor — in which the annulus wall flow interacts with the mainstream flow — have a major influence on its efficiency and surge margin. Despite many attempts over the years to predict the very complex flow patterns in the endwall regions, current compressor design methods still rely largely on empirical estimates of the aerodynamic losses and flow angle deviations in these regions. This paper describes a new phenomenological model of the key endwall flow phenomena treated in a circumferentially-averaged way. It starts from Hirsch and de Ruyck’s annulus wall boundary layer approach, but makes some important changes. The secondary vorticities arising from passage secondary flows and from tip clearance flows are calculated. Then the radial interchanges of momentum, energy and entropy arising from both diffusion and convection are estimated The model is incorporated into a streamline curvature program. The empirical blade force defect terms in the boundary layers are selected from cascade data. The effectiveness of the method is illustrated by comparing the predictions with experimental results on both low speed and high speed multistage compressors. It is found that the radial variation of flow parameters is quite well predicted, and so is the overall performance, except when significant endwall stall occurs.
A Spinning Finite Beam Element of General Orientation Analyzed With Rayleigh/Timoshenko/Saint-Venant Theory
Authors: Abrahamsson Thomas J. S. , Sällström Jan Henrik
Published: February 2015

Linear vibrations are studied for a straight uniform finite beam element of general orientation spinning at a constant angular speed about a fixed axis in the inertial space. The gyroscopic and circulatory matrices and also the geometric stiffness matrix of the beam element are presented. The effect of the centrifugal static axial load on the bending and torsional dynamic stiffnesses is thereby accounted for. The Rayleigh/Timoshenko/Saint-Venant theory is applied, and polynomial shape functions are used in the construction of the deformation fields. Non-zero off-diagonal elements in the gyroscopic and circulatory matrices indicate coupled bending/shearing/torsional/tensional free and forced modes of a generally oriented spinning beam. Two numerical examples demonstrate the use and performance of the beam element.
Nonlinear Analysis of Rotordynamic Instabilities in High-Speed Turbomachinery
Authors: Chan Dennis S. H.
Published: February 2015

A nonlinear approach based on the method of averaging has been developed to study unstable lateral vibrations of rotors in high-speed turbomachinery. The method makes use of an extended concept of bearing dynamic coefficients which are defined by applying small perturbations to the dynamic equilibrium positions. It has been applied to determine the stability threshold of flexible rotors supported on short and tilting-pad journal bearings respectively. Stability performance of systems supported on short journal bearings is improved by the presence of mass unbalance. However, for flexible rotors supported on tilting-pad journal bearings, increased unbalance can lead to lower rotordynamic stability margins. This has the significant implication that stability estimates from linear analysis are not always conservative. The present method provides a computationally more efficient way to better understand the nonlinear vibration behaviour of high-speed turbomachinery.
Three-Dimensional Navier-Stokes Analysis of a Two-Stage Gas Turbine
Authors: Arnone Andrea , Benvenuti Erio
Published: February 2015

A three-dimensional Navier-Stokes solver has been extended to include multi-row capability. The coupling between the various rows is implemented by means of mixing planes. Those planes are handled by retaining the radial distortions while mass-averaging in the pitch-wise direction. The code is applied to a two-stage, heavy-duty gas turbine at design conditions. A comparison of pitch-averaged quantities between blade rows with preliminary measurements and with through flow analysis is presented along with a discussion of the flow features in terms of secondary flows. Using roughly half a million grid points, an operating condition can be examined in about an hour on a modem supercomputer.
A CFD Assessment of Entrance Area Distributions in a Centrifugal Compressor Vaneless Diffuser
Authors: Sorokes James M.
Published: February 2015

The paper presents the results of a CFD study that assessed the various area distributions typically found in impeller / diffuser transitions in industrial centrifugal compressor stages. Results for two transition area schedules are compared. The findings agree with recently published data and suggest that problems exist in some standard configurations that could lead to rotating stall in the downstream vaneless diffuser.
The Development and Testing of the MFT8 Gas Turbine
Authors: Akagi K. , Uematsu K. , Yashlki T. , Horner J. , Krivichi K.
Published: February 2015

The MFT8 rated at 33,000 ps has been developed by Mitsubishi Heavy Industries (MHI) in support of the Techno SuperLiner (TSL) R&D program. The MFT8 combines the GG8 Gas Generator from Pratt & Whitney/Turbo Power & Marine with a new 3 stage, 5000 RPM, cantilevered rotor power turbine which was designed by MHI specifically for the TSL program and other high speed marine craft applications. This paper illustrates the versatility that an independent, two shaft gas generator offers in developing a new product for a specific application. The text describes the design philosophy, power turbine and controls simulation approach followed by the presentation of the model and power testing results as compared to the predicted parameters.
Application of Magnetic Bearings for Offshore Turboexpanders
Authors: Galelli Jean-Louis , de L’Hermite Hubert
Published: February 2015

This article describes the main design features and project stages of the first application of magnetic bearings for offshore turbomachinery.
Set up and Operation of a Recirculating Wetted Rigid Media Evaporative Cooler Installed in a Gas Turbine Combustion Inlet Air System
Authors: Johnson R. S.
Published: February 2015

A procedure for setting up and operating a recirculating evaporative cooler installed in the combustion air inlet system of a gas turbine is described. The procedure includes a recommendation for selecting the ambient operating wet and dry bulb temperatures. A description of the parameters used in the procedure and calculation methods are shown. In response to frequent inquiries about the rate at which water hardness (and elemental concentrations) increases with time, an equation to evaluate this increase with time is introduced. The time rate of change of water hardness and elemental concentrations for various blow-down rates and operating times are also evaluated.
Experimental Determination of Damping in Rolling Bearing Joints
Authors: Zeillinger Robert , Springer Helmut , Köttritsch Hubert
Published: February 2015

Equivalent radial stiffness and damping coefficients of ball bearing joints are identified from a bearing test rig through measured linear frequency domain transfer functions. Common least square techniques are used to curve fit analytical transfer functions of a MDOF-mechanical model of the test rig to the measured transfer functions. Both, the damping caused within the dry Hertzian contacts between the balls and the raceways and the damping within the bearing to housing interface are determined separately. A substantial interface damping is observed that may explain significant deviations between theoretical and experimental results stated in the literature.
Preferred Propagation Patterns in Surface Cracks Under Cyclic Loading
Authors: Gera Dinesh
Published: February 2015

There is a dramatic change in the shape of the semi-elliptical cracks growing due to combined cyclic bending and tensile loading of plates. The growing cracks change their shape such that they follow preferred propagation patterns (PPPs). It is observed that computation of strain energy release rate (G) in surface cracks plays an important role in determining the preferred propagation pattern (PPP). Numerical integration techniques have been employed to compute total strain energy (TSE) release rate. The variation of TSE with crack depth (a/t) for different bending ratios (Rb) is presented and discussed. A program in BASIC is written to directly simulate the propagation of crack on the screen. It is shown that for a given cyclic loading field, the PPP represents an upper limit on the aspect ratio of any surface crack growing due to this cyclic loading.
Advanced Digital 200 Chanels Dynamic Cassette Recording System for Development Engine Test Cell
Authors: Eyraud J. , Auzolle F.
Published: February 2015

The development of a new aircraft engine leads to equip development engine with a large number of dynamic transducers.

The huge flow of data generated in this type of test cannot be handled anymore practically through the conventional analog recording systems.

Recent emergence on the market of standardized multivendor ANSI ID1 high capacity, high speed digital recorders has allowed the development of a fully digital recording system at a competitive price. Such a system is able to complete in one sequence a full dynamic test measurement on a development engine through a 200 channels capacity.

A test cell is now being equipped and the expected benefits in terms of accuracy, productivity, lower cost and reduced volume of tape, have been achieved.

Standardized tapes permit data exchange between partners on an engine program.

Higher integration with data post-processing has also been obtained and transmission of data through fiber optic link is now made possible.
Hybrid Ceramic Bearing Development for Gas Turbine Engines
Authors: Slaney Frederick D.
Published: February 2015

Over the past seven years, an extensive hybrid bearing development program has been conducted at Textron Lycoming. This paper will report the details of testing and the extraordinary results which can be obtained with silicon nitride balls as applied in hybrid bearings on gas turbine engines. This paper describes the analytically predicted advantages which low mass silicon nitride balls offer at speeds over 2.0MDN. Rig testing comparing hybrid bearings to standard bearings is reported. Testing included heat generation evaluation which showed that hybrid bearings generate an average of 40% less heat than standard bearings.

Rig simulation of the AGT1500 mission duty cycle demonstrated that the hybrid silicon nitride bearing system is robust enough to handle the most severe operating conditions. Testing under severe slipping/skidding conditions demonstrated good resistance to skid failure. Under conditions selected to produce high wear, no wear was induced in a hybrid bearing while severe wear was induced in the M50 steel bearing. These preliminary successes lead to active engine testing on the AGT1500 and a new test program to demonstrate operation at 4.0 MDN.

As a result of these programs Textron Lycoming now considers hybrid ceramic bearings as a viable design to be used in high speed development applications. This paper provides design detail and test data covering the work outlined above.
Cautions for Polar-Plot Balancing Using Measurements Taken Near Fluid-Lubricated Bearings
Authors: Bently Donald E. , Hatch Charles T. , Franklin Wesley D.
Published: February 2015

The influence of fluid dynamic forces in a fluid-lubricated bearing on the imbalance response of a flexible rotor is examined with respect to effects on polar-plot balancing. The results of an experiment clearly demonstrate a journal phase lag at the center of the bearing which approaches 90° relative to the response of a mid-span massive disk over a range of rotor speeds from well below to well above the first lateral bending mode natural frequency of the rotor. The experimental phase lag is nearly constant over the entire range of rotor speeds. The results of this experiment are found to be in good agreement with results from both an analytical 2-degree-of-freedom model and a finite element analysis. The analytical model reveals that the severity of the phase lag effect is related to the ratio of the Quadrature Dynamic and Direct Dynamic stiffnesses acting at the journal. Calibration-weight balancing is found to be unaffected by the phase lag problem. The authors conclude that, - unless this phase lag is taken into account, polar-plot balancing may be difficult when vibration data from a relatively flexible rotor are obtained very close to a fluid-lubricated bearing.
The Development of Cost Effective Gas Turbine Installations Offshore
Authors: Hancock William P.
Published: February 2015

The paper describes the application and development of the offshore gas turbine from its infancy on Lake Maracaibo, Venezuela up to the current mature technology. North Sea developments are described, particularly in the Norwegian sector which was an important contributor to advancing the state of the art.

The first application of the second generation aero engine and of the very high pressure centrifugal gas compressor were important milestones which have made significant contributions to the economic recovery of North Sea hydrocarbons.

The author describes the current efforts to further optimise gas turbine installation, and operating costs. Cheaper and lighter gas turbine facilities require, not only increases in specific power, but also considerable innovation from the Engineers responsible for the application of this machinery.

For the future, fewer units of even larger ratings are foreseen, applied as high efficiency simple cycles with limited heat recovery.
Uncoupling of Vibration Modes Applied to Rotor Balancing
Authors: Delgado Eduardo Preciado , Romano Jorge Enrique Aguirre
Published: February 2015

It is argued in this paper that errors in rotor balancing practice are often due to the difference between the angular location of vibration transducers and that of the vibration modes of the rotor.

A methodology is presented for uncoupling of the vibration modes of an unbalanced rotor. This leads to the theoretical elimination of the errors in determining the phase angle of the resonant response of the rotor and hence in the angular location of the balancing weights.

Differences between theory and reality are here briefly discussed although field application methodologies and experiences will be the subject of another paper.
Performance of Worn Labyrinth Seals
Authors: Zimmerman H. , Kammerer A. , Wolff K. H.
Published: February 2015

The major sealing device between rotating and static aeroengine parts is still of labyrinth type. Nowadays the fins and the stator may be coated and the running conditions very often cause heavy rubs which leads to severe surface imperfections.

This paper investigates the influence of rounded fins and worn coatings on the discharge coefficients of straight through labyrinth seals. The relevant effects of Reynolds number are investigated.

Some measured fin and coating surfaces from engine parts are presented. Experimental and numerical results show a strong effect of wear on labyrinth seal performance.
Flow Analyses in a Single-Stage Propulsion Pump
Authors: Lee Yu-Tai , Hah Chunill , Loellbach James
Published: February 2015

Steady-state analyses of the incompressible flow past a single-stage stator/rotor propulsion pump are presented and compared to experimental data. The purpose of the current study is to validate a numerical method for the design application of a typical propulsion pump and for the acoustic analysis based on predicted flowfields. A steady multiple-blade-row approach is used to calculate the flowfields of the stator and the rotor. The numerical method is based on a fully conservative control-volume technique. The Reynolds-averaged Navier-Stokes equations are solved along with the standard two-equation k-ε turbulence model. Numerical results for both mean flow and acoustic properties compare well with measurements in the wake of each blade row. The rotor blade has a thick boundary layer in the last quarter of the chord and the flow separates near the trailing edge. These features invalidate many Euler prediction results. Due to the dramatic reduction of the turbulent eddy viscosity in the thick boundary layer, the standard k-ε model cannot predict the correct local flow characteristics near the rotor trailing edge and in its near wake. Thus, a modification of the turbulence length scale in the turbulence model is applied in the thick boundary layer in response to the reduction of the turbulent eddy viscosity.
Inverse Design of Centrifugal Compressor Vaned Diffusers in Inlet Shear Flows
Authors: Zangeneh M.
Published: February 2015

A 3D inverse design method in which the blade (or vane) geometry is designed for specified distributions of circulation and blade thickness is applied to the design of centrifugal compressor vaned diffusers. Two generic diffusers are designed, one with uniform inlet flow (equivalent to a conventional design) and the other with a sheared inlet flow. The inlet shear flow effects are modelled in the design method by using the so-called “Secondary Flow Approximation” in which the Bernoulli surfaces are convected by the tangentially mean inviscid flow field. The difference between the vane geometry of the uniform inlet flow and non-uniform inlet flow diffusers is found to be most significant from 50% chord to the trailing edge region.

The flow through both diffusers are computed by using Denton’s 3D inviscid Euler solver and Dawes’ 3D Navier-Stokes solver under sheared inflow conditions. The predictions indicate improved pressure recovery and internal flow field for the diffuser designed for shear inlet flow conditions.
Theoretical Model of the Spanwise Mixing Caused by Periodic Incoming Wakes
Authors: Imanari K.
Published: February 2015

A theoretical model is proposed for the spanwise mixing caused by periodic incoming wakes in the context of turbulent diffusion in axial-flow compressors prior to repeating-stage conditions. The model was used to predict the spanwise mixing coefficients across a stator of a single-stage compressor without IGVs. The correctness of the theory was demonstrated by the results that the predicted values were in good agreement with the associated experimental data.
Transient Process of Rotating Stall in Radial Vaneless Diffusers
Authors: Watanabe H. , Konomi S. , Ariga I.
Published: February 2015

This paper describes the process of rotating stall inception in a radial vaneless diffuser. Unsteady flow and rotating stall were investigated by measuring the wall static pressures and velocity distributions using X hot-wire probe. From the measurements of the velocity fluctuation, it is confirmed that the periodical disturbance in the reverse flow region as the prestall symptom occurs prior to the onset of stall and then the growth of that periodical disturbance leads to the rotating stall with fully developed non axisymmetric reversed flow. On the process of the rotating stall inception, reverse flow regions in the diffuser grow from the diffuser exit toward the inlet along the shroud and hub wall, and the rotating stall occurs when the reverse flow region on the shroud wall reaches to the impeller exit. In this paper, the effects of the diffuser exit blockage on the process of stall inception were also described. The flow rate of stall onset is moved to the lower side by the restriction of the diffuser exit width, however, this restriction does not affect the distribution of the reverse flow regions. That restriction suppresses the prestall disturbance in the reverse flow regions and then stabilize the flow in the diffuser.
Comparison of Calculated and Measured Heat Transfer Coefficients for Transonic and Supersonic Boundary-Layer Flows
Authors: Hürst C. , Schulz A. , Wittig S.
Published: February 2015

The present study compares measured and computed heat transfer coefficients for high speed boundary layer nozzle flows under engine Reynolds-number conditions (U∞ = 230 ÷ 880 m/s, Re* = 0.37 ÷ 1.07 · 106). Experimental data have been obtained by heat transfer measurements in a two-dimensional, non-symmetric, convergent-divergent nozzle. The nozzle wall is convectively cooled using water passages. The coolant heat transfer data and nozzle surface temperatures are used as boundary conditions for a three-dimensional finite-element code which is employed to calculate the temperature distribution inside the nozzle wall. Heat transfer coefficients along the hot gas nozzle wall are derived from the temperature gradients normal to the surface. The results are compared with numerical heat transfer predictions using the low Reynolds-number k-ε turbulence model by Lam and Bremhorst. Influence of compressibility in the transport equations for the turbulence properties is taken into account by using the local averaged density. The results confirm that this simplification leads to good results for transonic and low supersonic flows.
The Coefficient of Discharge of 30° Inclined Film Cooling Holes With Rounded Entries or Exits
Authors: Hay N. , Lampard D. , Khaldi A.
Published: February 2015

The coefficients of discharge of 30° inclined holes having a length to diameter ratio of 6, and rounded entries or exits have been measured for a range of crossflow conditions. The rounding radius varied from 0 to 1 hole diameters, and the crossflow Mach numbers from 0 to 0.5.

Rounding the hole inlet was found to be beneficial, with increases of up to 15% being obtained at high coolant (inlet) side crossflow Mach numbers. Rounding the exit produced no significant benefit.

The crossflow effects have been correlated using inlet and outlet additive loss coefficients. These reflect the changes in pressure drop across the hole necessary to maintain the hole mass flow rate when crossflows are applied.

The correlated data have been incorporated in a computer program which gives good predictions of discharge coefficient in the presence of either a coolant crossflow or a mainstream crossflow or both.
Cruise Gas Turbine Experience in the British and Netherlands Navies
Authors: Tasker R. J. , Schipholt M. G. Lutje
Published: February 2015

The views and opinions expressed in this paper are not necessarily endorsed by the Ministry of Defense.

The Royal Navy (RN) and the Royal Netherlands Navy (RNLN) use the Rolls Royce Tyne RN 1C Gas Turbine as their cruise propulsion engine, achieving some 150,000 running hours per year. Each installed Tyne engine achieves approximately 1800 running hours per year with a large proportion at high powers. This paper describes the experience of usage, the maintenance and technical control of these engines in recent years. and gives examples of actions taken and the results achieved.

The conclusions give an assessment of the general performance of the RN/RNLN team and the likely way ahead.
Development of 12CR Steel Disc for Heavy Duty Gas Turbines
Authors: Hidaka K. , Shiga M. , Nakamura S. , Fukui Y.
Published: February 2015

This paper describes research and development of 12Cr steel for heavy duty gas trubine disc. The 1300°C class gas turbine developed by Hitachi, Ltd. (H25) is commercially operated for land-based power generator (25MVA) which is realized after five years designing.

The quantitative study of alloying elements, which increase mechanical properties such as creep rupture strength, tensile strength, and toughness, is discussed. The sixteen pieces of real scale disc for 1300°C class gas turbine are examined to evaluate mechanical properties in terms of real operation. The recent study of 12Cr steel disc for 1500°C class gas turbine is also discussed.
Modeling for Control of Rotating Stall in High Speed Multi-Stage Axial Compressors
Authors: Feulner Matthew R. , Hendricks Gavin J. , Paduano James D.
Published: February 2015

Using a two dimensional compressible flow representation of axial compressor dynamics, a control-theoretic input-output model is derived which is of general utility in rotating stall/surge active control studies. The derivation presented here begins with a review of the fluid dynamic model, which is a 2D stage stacking technique that accounts for blade row pressure rise, loss and deviation as well as blade row and inter-blade row compressible flow. This model is extended to include the effects of the upstream and downstream geometry and boundary conditions, and then manipulated into a transfer function form that dynamically relates actuator motion to sensor measurements. Key relationships in this input-output form are then approximated using rational polynomials. Further manipulation yields an approximate model which is in standard form for studying active control of rotating stall and surge. As an example of high current relevance, the transfer function from an array of jet actuators to an array of static pressure sensors is derived. Numerical examples are also presented, including a demonstration of the importance of proper choice of sensor and actuator locations, as well as a comparison between sensor types. Under a variety of conditions, it was found that sensor locations near the front of the compressor or in the downstream gap are consistently the best choices, based on a quadratic optimization criterion and a specific 3-stage compressor model. The modeling and evaluation procedures presented here are a first step toward a rigorous approach to the design of active control systems for high speed axial compressors.
Investigation of the Flow Field Downstream of a Turbine Trailing Edge Cooled Nozzle Guide Vane
Authors: Sieverding C. H. , Arts T. , Dénos R. , Martelli F.
Published: February 2015

A trailing edge cooled low aspect ratio transonic turbine guide vane is investigated in the VKI Compression Tube Cascade Facility at an outlet Mach number M2,i s=1.05 and a coolant flow rate ṁc/ṁg=3%. The outlet flow field is surveyed by combined total-directional pressure probes and temperature probes. Special emphasis is put on the development of low blockage probes. Additional information is provided by oil flow visualizations and numerical flow visualizations with a three-dimensional Navier-Stokes code. The test results describe the strong differences in the axial evolution of the hub and tip endwall and secondary flows and demonstrate the self-similarity of the mid-span wake profiles. According to the total pressure and temperature profiles the wake mixing appears to be very fast in the near-wake but very slow in the far-wake region. The total pressure wake profile appears to be little affected by the coolant flow ejection.
A Study on Low NOx Combustion in LBG-Fueled 1500°C-Class Gas Turbine
Authors: Nakata Toshihiko , Sato Mikio , Ninomiya Toru , Hasegawa Takeharu
Published: February 2015

Developing integrated coal gasification combined cycle systems ensures cost-effective and environmentally sound options for supplying future power generation needs. The reduction of NOx emissions and increasing the inlet temperature of gas turbines are the most significant issues in gas turbine development in an Integrated Coal Gasification Combined Cycle (IGCC) power generation systems. The coal gasified fuel, which is produced in a coal gasifier of air-blown entrained-flow type has calorific value as low as 1/10 of natural gas. Furthermore the fuel gas contains ammonia when a gas cleaning system is a hot type, and ammonia will be converted to nitrogen oxides in the combustion process of a gas turbine.

This study is performed in a 1500°C-class gas turbine combustor firing low-Btu coal-gasified fuel in IGCC systems. An advanced rich-lean combustor of 150-MW class gas turbine was designed to hold stable combustion burning low-Btu gas and to reduce fuel NOx emission that is produced from the ammonia in the fuel. The main fuel and the combustion air is supplied into fuel-rich combustion chamber with strong swirl flow and make fuel-rich flame to decompose ammonia into intermediate reactants such as NHi and HCN. The secondary air is mixed with primary combustion gas dilatorily to suppress the oxidization of ammonia reactants in fuel-lean combustion chamber and to promote a reducing process to nitrogen.

By testing it under atmospheric pressure conditions, the authors have obtained a very significant result through investigating the effect of combustor exit gas temperature on combustion characteristics. Since we have ascertained the excellent performance of the tested combustor through our extensive investigation, we wish to report on the results.
Emission and Performance of a Lean-Premixed Gas Fuel Injection System for Aeroderivative Gas Turbine Engines
Authors: Snyder Timothy S. , Rosfjord Thomas J. , McVey John B. , Hu Aaron S. , Schlein Barry C.
Published: February 2015

A dry-low-NOx, high-airflow-capacity fuel injection system for a lean-premixed combustor has been developed for a moderate pressure ratio (20:1) aeroderivative gas turbine engine. Engine requirements for combustor pressure drop, emissions, and operability have been met. Combustion performance was evaluated at high power conditions in a high-pressure, single-nozzle test facility which operates at full baseload conditions. Single digit NOx levels and high combustion efficiency were achieved A wide operability range with no signs of flashback, autoignition, or thermal problems was demonsuated. NOx sensitivities 10 pressure and residence time were found to be small at flame temperatures below 1850 K (2870 F). Above 1850 K some NOx sensitivity to pressure and residence Lime was observed and was associated with the increased role of the thermal NOx production mechanism at elevated flame temperatures.
Modelling the Transient Behavior of Combined Cycle Plants
Authors: Dechamps P. J.
Published: February 2015

The last decade has seen remarkable improvement in industrial gas turbine unit size and performances. The coming years and decades hold the promise of even more progress in these fields.

Simultaneously, the fuel utilization achieved by combined cycles has been steadily increased, which is a combination of improvements both in the gas turbine technology and in the new combined cycle schemes with multiple pressure levels.

These combined cycles quite often have to operate on a load cycling duty or in the intermediate load range, so that not only the design point performances but even the off design are sufficient to ensure the plant profitability. Its transient behaviour, its ability to start quickly and reliably, are key parameters when selecting the plant.

This paper describes a method developed for the calculation of the transient performances of combined cycles, from no load situations, including cold conditions, to full load. The method is then applied and illustrated with a recently commissioned plant, for which some transient measurements are available.
Numerical Study on Rotating Stall in Finite Pitch Cascades
Authors: Nishizawa Toshio , Takata Hiroyuki
Published: February 2015

Flow behavior of rotating stall in finite pitch cascades is discussed through numerical analyses by means of a vortex method, which is particularly developed to solve unsteady flows through stalled cascades. It is shown that stall vortex and unstall vortex are, shed from each stalled blade periodically, and the behavior of these vortices has considerable effects on various properties of rotating stall, such as magnitude of flow fluctuation, propagation velocity, the number of stall cells, and so on. When a rotating stall is initiated and developed in an isolated cascade at smaller inlet flow angles around the stall inception point, a plural number of stall cells tend to propagate on the growing process, although only one stall cell survives eventually in a fully developed rotating stall. At larger flow angles, a single stall cell splits into two separate cells as it propagates. These processes are found for the first time through the analyses of finite pitch cascades. With the inlet guide vanes upstream, a plural number of stall cells can grow in a fully developed rotating stall, and the number of stall cells depends on the exit flow angle of the guide vanes and the axial distance between the two cascades. The numerical results agree well with experiments.
Variations in the NOx Emission of Gas Turbines: Effects of Air Temperature, Air Humidity and Natural Gas Composition
Authors: Visser B. Martien , Bahlmann Fred C.
Published: February 2015

The NOx emission, produced by gas turbines varies with ambient conditions and with fuel gas composition. Often, legislation requires that the NOx emissions of gas turbines has to be corrected to standard conditions. The EPA formula may be used for the correction for ambient temperature and humidity. In the Netherlands, the correction for fuel-gas composition is based on the observation that for natural gases, NOx emission varies linearly with the Lower Calorific Value (LCV).

It is concluded that both the EPA and LCV correction formulas are equivalent to the following relation between flame temperature and NOx emission: NOxa=NOxb*(1.0065)Ta−Tb where Ta and Tb represent characteristic flame temperatures under conditions a and b. In the paper, the utility of the EPA and the LCV correction formulas for gas turbines equipped with modem lean-premixed combustors is discussed.
Large Engine Hybrid Ceramic Bearings
Authors: Rhoads Mark A. , Bashyam Manohar , Crecelius William J.
Published: February 2015

General Electric Aircraft Engines under contract from the Advanced Research Projects Agency (ARPA), has demonstrated the ability of ceramic rolling elements to withstand shock loading conditions experienced during race spalling, has performed a series of full scale tests directed at showing the thermal benefit of large hybrid bearings at speeds up to 3.0 MDN, and has developed a condition monitoring device that detects both ceramic and metallic bearing debris. The details of the three primary tasks are presented in this paper: Task 1 involves the testing of a hybrid bearing operating in severe shock loading conditions, with comparisons to an all steel bearing. Task 2 involves back-to-back comparison of an all-steel high speed bearing to a hybrid bearing of the same geometry and to a hybrid bearing of tighter race curvatures, showing differences between outer ring temperatures of all-steel and hybrid bearings. Task 3 deals with the bench testing of a new ultrasonic bearing condition monitoring device, designed to collect and detect both ceramic or metallic debris.
Direct Dynamic Testing of Stereolithographic Models
Authors: Dornfeld William H.
Published: February 2015

Model testing has long been used to validate, augment, or replace structural analysis. Choice of the extent of model usage depends on the time, budget, and skills available, and upon the complexity of the structure and the consequences of the results. In particular, plastic models have seen significant usage in understanding the static and dynamic behavior of many different industrial structures. Today’s ability to generate scaled plastic models directly from 3D CAD geometry models via stereolithography (SLA) has opened a new chapter on model testing. SLA models are easily size-scaled and quickly produced, and some SLA polymers have mechanical properties that are well suited for dynamic testing. The use of SLA models makes possible early testing and accelerated test development work that can reduce costs and shrink the product development cycle. This paper describes the elements of using SLA plastic models for dynamic testing, including size and frequency scaling. Examples of SLA applications at Textron Lycoming for rap/shaker testing and for holography are discussed.