bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Cooling Film Development Calculations for Transpiration Cooled Flat Plates With Different Turbulence Models
Authors: Bohn Dieter E. , Moritz Norbert 
Published: July 2014

A transpiration cooled flat plate configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The geometrical setup and the fluid flow conditions are derived from modern gas turbine combustion chambers. The plate is composed of three layers, a substrate layer (CMSX-4) with a thickness of 2 mm, a bondcoat (MCrAlY) with thickness 0,15 mm, and a thermal barrier coating (EB-PVD, Yttrium stabilized ZrO2) with thickness 0,25 mm, respectively.
The numerical grid contains the coolant supply (plenum), the solid body, and the main flow area upon the plate. The transpiration cooling is realized by finest drilled holes with a diameter of 0,2 mm that are shaped in the region of the thermal barrier coating. The holes are inclined with an angle of 30°. Two different configurations are investigated that differ in the shaping of the holes in their outlet region.
The numerical investigation focus on the influence of different turbulence models on the results. Regarding the secondary flow, the cooling film development and complex jet mixing vortex systems are analyzed. Additionally, the impact on the temperature distribution both on the plate surface and in the plate is investigated. It is shown that the choice of the turbulence model has a significant influence on the prediction of the flow structure, and, consequently, on the calculation of the thermal load of the solid body.
Approximate Solutions for Flow and Heat Transfer in Pre-Swirl Rotating-Disc Systems
Authors: Karabay Hasan , Wilson Michael , Owen J. Michael 
Published: July 2014

The paper presents approximate solutions of the momentum-integral equations for swirling flow in a rotating cavity, which is used to model a cover-plate pre-swirl rotating-disc system in a gas-turbine engine. The solutions give the variation of Cm, the moment coefficient on the rotating discs, with βp, the pre-swirl ratio of the cooling air. Cm decreases from the free-disc value at βp = 0 to zero at βp = βp,crit, and becomes negative when βp > βp,crit. Using the Reynolds analogy, the theoretical distribution of Cm is used to calculate Nuav, the average Nusselt number on the heated disc. This shows that Nuav has a minimum value when βp = βp,crit.
The approximate solutions of Cm and Nuav are compared with computed values obtained using an axisymmetric elliptic solver. For most of the conditions considered, the theoretical values of Cm are in good agreement with the computed values. However, unlike the approximate solutions, the computed values of Cm show some dependency on the coolant flow rate. There is reasonable agreement between the theoretical and computed distribution of Nuav provided βp < βp,crit. Near βp,crit there are discontinuities in the computed values, and for larger values of βp, where the Reynolds analogy may be invalid, the theoretical and computed variations of Nuav tend to diverge.
VECTRA™ Power Turbine Development Program
Authors: deBeer Bruce R. , Nye David A. 
Published: July 2014

Dresser-Rand developed the VECTRA-40 power turbine specifically for the LM2500+ gas generator. This “clean sheet of paper” design uses some of the best features from both aeroderivative and heavy duty gas turbines. After the design phase was complete, an extensive development program was undertaken to confirm that both the mechanical and aerodynamic design objectives were met. Two units were built, instrumented, and tested to full load. In addition, several components were rig tested to verify stiffness, natural frequency, or operating characteristics. Finally, some events that could not be physically tested, such as blade out response, were tested virtually.
During development testing, the power turbine was extensively instrumented with state-of-the-art sensors to verify the mechanical design and aerodynamic performance of the VECTRA. A PC based data acquisition system (DAQ) was constructed to simultaneously acquire and record over 1000 individual channels of data. Instrumentation was installed to record the mechanical responses and operating temperatures of all rotating components, as well as critical stationary components. Other groups of instrumentation were used to verify flowpath performance, cooling air distribution, and lubrication system operation. The physical devices connected to the DAQ system ranged from industrial transducers and signal conditioners to an innovative external telemetry system for rotating thermocouples and dynamic strain gages.
The VECTRA is a high speed power turbine that was initially designed for mechanical drive applications. However recent component testing and full load testing of two units in generator drive packages have demonstrated that it is also well suited for power generation applications.
Series or Parallel Arrangement in a Two-Unit Compressor Station
Authors: Ohanian Sebouh , Kurz Rainer 
Published: July 2014

This paper discusses how to determine the arrangement of compressors in a two-unit gas pipeline station where there is no standby unit. The compressors are driven by variable speed drivers such as gas turbines or variable frequency electric motors.
Both series and parallel arrangements are analyzed in a transient simulation mode to determine which operation mode is more advantageous.
Among the assumptions in this paper are the performance characteristics of the compressor. It will be outlined how these performance characteristics influence the conclusions.
Increase of Global Efficiency in Pipeline Compression Station: A Challenge for the Future
Authors: Pucci Marco , Guzzardi Maria Germana , Saccardi Giovanni 
Published: July 2014

The article, after a short market analysis of the gas sector, deals with the subjects relative to the increase of efficiency and at the same time to the minimisation of global environmental impact in pipeline gas compression stations with gas turbine driver.
In the second part, the article deals with the analysis of one of the new possible solutions in new or repowering/revamping projects of pipeline compression stations: the utilization of gas-steam combined cycle technology, focusing attention on the key issues of this kind of industrial plants, such as high availability and high flexibility in gas compressor, safety operation, possibility of remote operation and easy maintenance.
In particular, the article will analyze a specific project: the Transitgas Ruswil Extension Compressor Project, an example of implementation of these new particular plants, which we do believe to be an answer to the future challenge of optimisation of global efficiency.
Effects of Wheel-Shaft-Fluid Coupling and Local Wheel Deformations on the Global Behavior of Shaft Lines
Authors: Lornage D. , Chatelet E. , Jacquet-Richardet G. 
Published: July 2014

Rotating parts of turbomachines are generally studied using different uncoupled approaches. For example, the dynamic behavior of shafts and wheels are considered independently and the influence of the surrounding fluid is often taken into account in an approximate way. These approaches, while often sufficiently accurate, are questionable when wheel-shaft coupling is observed or when fluid elements are strongly coupled with local structural deformations (leakage flow between wheel and casing, fluid bearings mounted on a thin-walled shaft, etc.). The approach proposed is a step toward a global model of shaft lines. The whole flexible wheel-shaft assembly and the influence of specific fluid film elements are considered in a fully three-dimensional model.
In this paper, the proposed model is first presented and then applied to a simple disc-shaft assembly coupled with a fluid film clustered between the disc and a rigid casing. The finite element method is used together with a modal reduction for the structural analysis. As thin fluid films are considered, the Reynolds equation is solved using finite differences in order to obtain the pressure field. Data are transferred between structural and fluid meshes using a general method based on an interfacing grid concept. The equations governing the whole system are solved within a time marching procedure.
The results obtained show significant influence of specific 3D features such as disc-shaft coupling and local disc deformations on global behavior.
Using Guided Balls to Auto-Balance Rotors
Authors: Wettergren Håkan L. 
Published: July 2014

By using balancing balls constrained to move in a circular groove filled with oil, the vibration of rotating machinery can, under certain circumstances, be reduced. This paper shows that the damping from the oil reduces the instability region, i.e. the conditions when the balancing balls don’t find their equilibrium positions. However, the instability region seems to increase with increasing number of balancing balls.
The critical ball damping ratio is highest just above the natural frequency and then rapidly decreases. Consequently, since the region between instability and critical damping is quite small, the ball damping should be made as small as possible without getting too close to the instability threshold.
Bearing damping has a large effect on the instability region. High bearing damping will suppress the instability.
The time it takes to reach the asymptotically stable position seems to increase with increasing number of balls. Keeping this time low is one of the most important things when designing a balancing ring.
Numerical Unsteady Flow Analysis of a Turbine Stage With Extremely Large Blade Loads
Authors: Jöcker Markus , Hillion Francois X. , Fransson Torsten H. , Wåhlén Ulf 
Published: July 2014

This paper presents the detailed numerical analysis including parametric studies on the aerodynamic excitation mechanisms in a turbine stage due to the unsteady stator-rotor interaction. The work is part of the pre-design study of a high pressure subsonic turbine for a rocket engine turbopump. The pressure level in such turbines can be remarkably high (in this case 54 MPa inlet total pressure). Hence, large unsteady rotor blade loads can be expected, which impose difficult design requirements.
The parameter studies are performed at midspan with the numerical flow solver UNSFLO, a 2D/Q3D unsteady hybrid Euler/Navier-Stokes solver. Comparisons to 2D and steady 3D results obtained with a fully viscous solver, VOLSOL, are made.
The investigated design parameters are the axial gap (∼8%–29% of rotor axial chord length) and the stator vane size and count (stator-rotor pitch ratio ∼1–2.75). For the nominal case the numerical solution is analyzed regarding the contributions of potential and vortical flow disturbances at the rotor inlet using rotor gust computations.
It was found that gust calculations were not capable to capture the complexity of the detected excitation mechanisms, but the possibility to reduce excitations by enforcing cancellation of the vortical and potential effects has been elaborated. The potential excitation mechanism in the present turbine stage is found dominant compared to relatively small and local wake excitation effects. The parameter studies indicate design recommendations for the axial gap and the stator size regarding the unsteady rotor load.
Approach to Unidirectional Coupled CFD – FEM Analysis of Axial Turbocharger Turbine Blades
Authors: Filsinger D. , Szwedowicz J. , Schäfer O. 
Published: July 2014

This paper describes an approach to unidirectional coupled CFD – FEM analysis developed at ABB Turbo Systems Ltd.. Results of numerical investigations concerning the vibration behavior of an axial turbocharger turbine are presented. To predict the excitation forces acting on the rotating blades, the time resolved two-dimensional coupled stator - rotor flow field of the turbine stage was calculated. The unsteady pressure, imposed on the airfoil contour, leads to circumferentially non-uniform and pulsating excitation forces acting on the rotating bladed disc.
A harmonic transformation of the excitation forces into the rotating co-ordinate system of a single blade was elaborated and the complex Fourier amplitudes were determined. The bladed rotor was modeled by a single symmetric segment with complex circumferential boundary conditions. With respect to different nodal diameter numbers free vibration analyses of the disc assembly were then effectively performed. For calculated resonance conditions, the steady state responses of the turbocharger bladed disc were computed. By using this coupled CFD - FEM analysis, the dynamic loading of the turbine blades can be determined in the design process.
Analysis of the Worst Mistuning Patterns in Bladed Disc Assemblies
Authors: Petrov E. P. , Ewins D. J. 
Published: July 2014

In the paper, the problem of determining of the worst mistuning patterns is formulated and solved as an optimization problem. Maximum resonant amplitudes searched across the many nodes of a large-scale finite element model of a mistuned bladed disc and across all the excitation frequencies in a given range are combined into an objective function. Individual blade mistuning is controlled by varying design parameters, whose variation range is constrained by manufacture tolerances.
Detailed realistic finite element models, which have so far only been used for analysing tuned bladed discs, are used for calculation of the forced resonant response of mistuned assemblies and for determination of its sensitivity coefficients with respect to mistuning variation.
Results of the optimum search of mistuning patterns for some practical bladed discs are analysed and reveal higher worst cases than those found in previous studies.
Stall Inception in a High-Speed Centrifugal Compressor
Authors: Kang Jeong-Seek , Kang Shin-Hyoung 
Published: July 2014

Stall inception in a high-speed centrifugal compressor has been examined. The main objective was to find stall precursor and to develop a reliable stall warning method. Eight equally spaced fast-response pressure transducers in the inducer detected the spatial structure of small amplitude perturbations, via spatial Fourier transform, as stall is approached. Near the stall inception point, the phase of spatial Fourier coefficients increased linearly with the speed of impeller rotation for several impeller revolutions at all test speeds, and the spectrum at impeller frequency increased as stall is approached. This is the clear evidence that the impeller frequency participates in the stalling process.
For stall warning, a method which uses the spectrum at impeller frequency is suggested. The use of spectrum at impeller frequency as a stall warning method showed a warning time of about two hundreds impeller revolutions. This method uses only one sensor that it has made the stall warning method more useful. And the well-known traveling wave energy method proved to be a good method for stall warning also in a high-speed centrifugal compressor. The warning time was about one hundred impeller revolutions at lower speeds, and about one thousand impeller revolutions at higher speeds. The stall warning methods used here were found to be robust and reliable. Therefore, it seems to be promising to set up a reliable stall avoidance control based on this analysis.
Numerical Investigation of Airfoil Clocking in a Three-Stage Low Pressure Turbine
Authors: Arnone Andrea , Marconcini Michele , Pacciani Roberto , Schipani Claudia , Spano Ennio 
Published: July 2014

A quasi–three–dimensional, blade–to–blade, time–accurate, viscous solver w as used for a three–stage LP turbine study Due to the low Reynolds number, transitional computations were performed. Unsteady analyses were then carried out by varying the circumferential relative position of consecutive vanes and blade rows to study the effects of clocking on the turbine’s performance. A clocking strategy developed in order to limit the number of configurations to be analyzed is discussed. The optimum analytically–determined clocking position is illustrated for two different operating conditions, referred to as cruise and takeoff.
The effects of clocking on wake interaction mechanisms and unsteady blade loadings is presented and discussed. For low Reynolds number turbine flows, the importance of taking transition into account in clocking analysis is demonstrated by a comparison with a fully turbulent approach.
Unsteady Aerodynamical Blade Row Interaction in a New Multistage Research Turbine: Part 1 — Experimental Investigation
Authors: Gombert Ralf , Höhn Wolfgang 
Published: July 2014

Exploitation of stator–stator interaction phenomena can increase overall efficiency in axial turbomachines. The first part of this paper sets out to present results of steady and unsteady flow experiments obtained in a new three stage cold flow low pressure turbine. Observation and understanding of boundary layer development and transition phenomena on the vanes dependent on relative stator position will be the focal point. In addition to this, stator position influence on profile loss, turbine efficiency and the development of secondary flow are examined.
The experiments were carried out in the closed circuit test bed of the Institute of Aeronautical Propulsion at Stuttgart University. Annulus geometry and blading design of the research turbine were taken from the low pressure turbine of a modern commercial jet engine. The three stage test rig had identical blade counts for all stators or rotors respectively, whilst the circumferential position of each stator row could be individually adjusted. The second and third stators were optimised with respect to the radial alignment of the vanes. Surface mounted hot film gauges on the vanes and hot film probes were employed to assess the unsteady interaction phenomena. For steady measurements, pneumatic five hole probes and multiple kielhead pressure and temperature probes were used.
For both the second and third stator, circumferential position was varied in eight steps over one pitch. Whereas the design point forms the basis of this detailed investigation, some attention was also paid to variations in Reynolds number and wheel speed. The results, such as quasi wall shear stress, stochastic and periodic fluctuations, total pressure etc., are presented in the form of chordwise ensemble-averaged distributions and contour plots and should be compared with the corresponding numerical studies presented in the second part of this paper.
Unsteady Aerodynamical Blade Row Interaction in a New Multistage Research Turbine: Part 2 — Numerical Investigation
Authors: Höhn Wolfgang , Gombert Ralf , Kraus Astrid 
Published: July 2014

This paper is the second part of a two part paper, which describes in part one the experimental setup and results of a new multistage turbine. Part two presents results of unsteady viscous flow calculations based on cold flow experiments of that three stage low pressure turbine. The present paper emphasizes the investigation of stator-stator interaction of a low pressure turbine section of a commercial jet engine. Different positions for the second and third stator are studied numerically and experimentally with respect to the blade row interaction, unsteady blade loading and unsteady boundary layer effects.
A time accurate Reynolds averaged Navier-Stokes solver is applied for the computations. Turbulence is modeled using the Spalart-Allmaras one equation model turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed by a four stage Runge-Kutta scheme, which is accelerated by a two grid method in the viscous boundary layer around the blades and alternatively by a dual time stepping method. At the inlet and outlet reflecting or non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness.
In particular, the flow field with respect to time averaged and unsteady quantities such as surface pressure, vorticity, unsteady velocity field and skin friction are compared with the experiments conducted in the cold air flow test rig.
An Analysis of the Spatial Fluctuations at the Stator-Rotor Interface in a Transonic Turbine
Authors: Callot Stanislas , Ferrand Pascal 
Published: July 2014

This paper analyses the flow in a transonic turbine stage, using numerical results from a full 3D Navier-Stokes computation over the whole stage. This analysis, based on the combination of time and space Fourier transforms, points out how a spatio-temporal periodicity phenomenon is involved in the so-called stator-rotor interaction.
A first comparison is made between the computational results using geometrical approximation and the results achieved by the complete simulation. This analysis points out how the signal is enforced by the numerical conditions at the circumferential boundaries.
The stator-rotor interaction produces low spatial harmonics which are identified as spinning modes by means of Fourier series. The analytical theory from Tyler and Sofrin (1962) is then used to define a general model of stator-rotor interaction. This model allows the determination of the angular speed of rotation of the spinning modes, and results are compared with the global numerical simulation.
Finally, a first analysis of the axial propagation of the spinning modes is proposed, and attention is focused on the fact, that only few parameters are necessary to reproduce the unsteady signal.
Instability Analysis of a Centrifugal Compressor Stage Near Peak Pressure Rise
Authors: Jahnen Werner , Breugem Wim-Paul , Ribi Beat 
Published: July 2014

It is often observed that radial compressor stages exhibit different types of instabilities dependent on the rotor-diffuser matching. The onset of instability may be before, at, or after the slope of the pressure rise characteristic becomes zero during throttling. In this study the flow conditions in the individual stage components at instability onset have been investigated experimentally and theoretically to allow an improvement of present prediction methods.
Within the scope of the experimental study separate characteristics of the rotor and the diffuser have been recorded in detail while unsteady measurements have been performed simultaneously. The measurement results show that rotor and/or diffuser instability affects overall stage stability. The nature of stage component stability suggests that rotor and diffuser can be excited as subsystems.
For an improved understanding, numerical investigations based on the Moore-Greitzer (1986) model have been performed. In order to account for the observed subsystem properties of rotor and diffuser, the model had to be extended, and was adapted to the geometry of the investigated radial compressor stage. By implementing inner stage mass storage and flow redistribution capability into the model, a decoupled treatment of stage components was accomplished. The numerical results are in qualitative agreement with the measurements, and prove that a decoupled treatment of rotor and diffuser in radial compressor stages is able to describe stall inception more accurately.