bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of an Advanced Automated Knowledge Based Combustor Preliminary Design Process Suitable for Low NOx Combustion Systems Optimization
Authors: Gessel Maxim , Pfitzner Michael , Eggels Ruud 
Published: August 2015

Within the current combustor design process, the combustor performance and sizing is mainly estimated using Prelim Design Tools, which are based on empirical correlations. In order to investigate these preliminary designs in more detail, the application of CFD within the preliminary combustor design process has steadily increased. However, the generation of CFD solutions is a time consuming process, since it requires adapted CAD models and the generation of meshes before the actual CFD computations can be performed. Moreover, it has to be assured that the meshes are suitable for the computational code, which may require several iterations within the grid generation process. Next the manual setting of the boundary conditions for CFD is also prone to errors and the post-processing of the CFD results is generally time consuming. Therefore, an advanced approach of an automated preliminary combustor design process has been developed within the 7th framework of the European research project IMPACT-AE, based on the knowledge obtained in the 6th framework of the European research project INTELLECT D.M. The processes developed are based on improved and robust knowledge-based-engineering tools for modern low NOx combustor geometries.
The advanced approach comprises a KBE preliminary design tool with improved Rolls-Royce in-house design rules for modern low NOx high efficiency combustors. It is based on fully featured 3-D parametric combustor models, including the pre-diffuser, the injector, the flame tube and the casing parts. An unstructured automatable meshing-tool CFS BOXERMesh is used to generate high quality meshes. Subsequent CFD analyses are performed using an unstructured Rolls-Royce in-house combustion CFD code PRECISE-UNS and the post-processing is performed using the open source tool ParaView. The choice of these tools is based on their ability to be fully automated using appropriate scripts and information. To create a strong linkage between these tools a KBE interface-tool and a database were implemented. These tools manage the individual processes fully automatically, including e.g. the transfer of geometry parameters to the CAD models; the gathering of the combustion chamber dependent boundary conditions and numerical parameters for the CFD analysis; or the generation of tool-internal automation scripts, using interface-tool input and database information.
Several grid refinement studies were performed to define an automated mesh refinement strategy, using scaled cell sizes for each combustor feature. Furthermore, a mixing port diameter scaling and a detailed post-processing procedure are described.
Design of a High-Speed Rotating Test Rig for Adaptive Seal Systems
Authors: Beermann Laura S. , Höfler Corina , Bauer Hans-Jörg 
Published: August 2015

Gas turbine engines are subject to increased performance and improved efficiency, which leads to rising core temperatures with additional cooling needs. Reducing the parasitic leakage in the secondary flow system is important to meet the challenging requirements. New seal designs have to be tested and optimized at engine like conditions, like high pressure of up to 9 bar and surface speed of up to 280 m/s as well as an adjusted flow field. Flexible seal designs are an innovative approach to reduce leakage mass flows significantly. Axial and radial movements during transient operating conditions can be compensated easily, thus allowing a smaller gap width and minimizing rub and heat load.
This paper describes the design and construction of a new rotating test rig facility. To the knowledge of the authors, this is the only test rig with an adjustable gap width and flow field in a high pressure and speed range. The facility is capable of up to 8 bar differential pressure across the seal and up to 4 bar back pressure. The high revolution engine facilitates a surface speed of up to 280 m/s. A traversable casing allows a quick change of the gap width during operation and simulates radial and axial rotor/stator movements in the engine. The seal movement as well as the resulting gap width are measured during operation to fully understand the seal behavior.
An important feature of the new test rig is the continuously adjustable pre-swirl system. It has been designed to cover the different flow conditions in the real engine. Therefore, a RANS parameter study of the pre-swirl chamber has been conducted, which shows the adjustability of different pre-swirl ratios for constant and changing inlet mass flows.
1D Adaptive Measurement Grid for Improved Pneumatic Probe Measurements
Authors: Bartsch Christian , Hölle Magnus , Jeschke Peter , Metzler Timo 
Published: August 2015

The subject of this paper is a flow-adaptive measurement grid developed for pneumatic probe measurements in turbomachinery flows. The performance of the algorithm is demonstrated by a circumferential traverse at a constant radial position with a pneumatic 5-hole probe in an annular cascade wind tunnel. Compared to a conventional equidistant measurement grid, the algorithm automatically computes the amount of measurement points needed for a high resolution of the pressure distribution in steady flow fields. The algorithm is fully automated and approximates the pressure distribution of a preliminary transient measurement very accurately. Even though the spacing of the computed measurement points differs significantly from an equidistant grid, post-processing corrections related to the probe head geometry can still be applied. Accompanying a redistribution of the measurement points is a reduction in the overall points needed for the measurement. The commonly encountered problem of data oversampling is therefore avoided. Compared to a conventional equidistant measurement grid, the adaptive grid showed a significant reduction in the overall measurement points and a reduction in the duration of the measurement — while maintaining the accuracy in the computation of flow parameters.
The purpose of this paper is to demonstrate the performance of an automatic detection of measurement points so that valuable measurement time can be saved without a loss in quality of the obtained data.
On the Numerical Evaluation of Tone Noise Emissions Generated by a Turbine Stage: An In-Depth Comparison Among Different Computational Methods
Authors: Pinelli Lorenzo , Poli Francesco , Arnone Andrea , Guérin Sébastien , Holewa Axel , Fernández Aparicio José Ramón , Puente Ricardo , Torzo Davide , Favre Christophe , Gaetani Paolo , Persico Giacomo 
Published: August 2015

Within the European research project RECORD (Research on Core Noise Reduction) the tone noise emissions of a high-pressure turbine stage have been numerically evaluated by six different academic and industrial partners. The turbine stage geometry and operating conditions match an HPT test rig located at Politecnico di Milano (Italy).
Since the constant demand for quieter and greener propulsion systems has led to the development of several numerical aeroacoustic codes, this common benchmark represents an important chance to compare the performance of each approach.
In this paper, the tone noise results of three distinct categories of numerical solvers (unsteady RANS, harmonic balance and time-linearized approaches) are compared. For the tone noise simulations, all the partners used non-reflecting boundary conditions at the domain inlet and outlet in order to avoid spurious reflections.
Moreover, the acoustic modeshapes in the turbine duct were evaluated with different level of complexity by the various partners and different post-processing techniques were employed to extract the acoustic waves from the unsteady solutions.
The result comparisons for the blade passing frequency have shown a good agreement (within 4 dB) among the partners in terms of PWL values. Also the acoustic eigenmodes (radial shapes of the pressure waves) and the eigenvalues (axial wave numbers) agree well among the different simulations. A wide range of acoustic results are presented and discussed in the paper.
Experimental Study on the Friction Contact Between a Labyrinth Seal Fin and a Honeycomb Stator
Authors: Pychynski Tim , Höfler Corina , Bauer Hans-Jörg 
Published: August 2015

This paper presents results from an extensive experimental study on the rubbing behavior of labyrinth seal fins and a honeycomb liner. The objective of the present work is to improve the understanding of the rub behavior of labyrinth seals by quantifying the effects and interactions of sliding speed, incursion rate, seal geometry and seal fin rub position on the honeycomb liner. In order to reduce the complexity of the friction system studied, this work focuses on the contact between a single seal fin and a single metal foil. The metal foil is positioned in parallel to the seal fin to represent contact between the seal fin and the honeycomb double foil section. A special test rig was set up enabling the radial incursion of a metal foil into a rotating labyrinth seal fin at a defined incursion rate of up to 0.65 mm/s and friction velocities up to 165 m/s. Contact forces, friction temperatures and wear were measured during or after the rub event. In total, 88 rub tests including several repetitions of each rub scenario have been conducted to obtain a solid data base.
The results show that rub forces are mainly a function of the rub parameters incursion rate and friction velocity. Overall, the results demonstrate a strong interaction between contact forces, friction temperature and wear behavior of the rub system. The presented tests confirm basic qualitative observations regarding blade rubbing provided in literature.
Cross Wind Influence on Noise Emission and Computed Vibrational Noise of an Axial Fan
Authors: Heinemann Till , Münsterjohann Sven , Zenger Florian , Becker Stefan 
Published: August 2015

The total noise emissions of two commercial axial fans were measured in a semi-anechoic fan test rig in comparison. The total sound pressure levels and the respective spectra were found to change with the fans’ operating points. Increasing fan flow rates lowered the total acoustic pressure, with a broadband shift towards higher frequencies, keeping perceived (A-weighted) sound pressure levels approximately constant over a wide range of operating points. In a second step, Laser Scanning Vibrometry measurements of the fan blades’ axial motion were conducted in comparison inside a wind tunnel fan test rig. Rotating blade surface vibration data was used as sole input to a Ffowcs Williams and Hawkings algorithm, to estimate noise emission from vibration. The computed noise from surface vibration was found to be hardly affected by the change of fan flow rate.
In the application of an axial fan subject to natural wind or induced cross flow at its inlet, the flow field and possible noise emission of the fan changes. Microphone measurements of the cross flow influence inside a semi-anechoic wind tunnel revealed increasing broadband noise with ambient flow field velocity, and an amplification of the sound at the blade passing frequency harmonics. Similar excitations of the blade passing frequency harmonics under cross flow influence were also found in sound pressure spectra computations based on the Laser Scanning Vibrometry measurement data captured in the wind tunnel fan test rig. Blade vibration is considered to contribute to the low frequency tonal noise emission of axial fans operating under cross flow conditions.
Numerical Assessment of Fan-Ducting Coupling for Gas Turbine Ventilation Systems
Authors: Corsini Alessandro , Delibra Giovanni , Minotti Stefano , Rossin Stefano 
Published: August 2015

Gas turbines enclosures entail a high number of auxiliary systems which must be preserved from heat, ensuring therefore the long term operation of the internal instrumentation and of the data acquisition system. A dedicated ventilation system is designed to keep the enclosure environment sufficiently cool and dilute any gas coming from potential internal leakage to limiting explosion risks. These systems are equipped with axial fans, usually fed with air coming from the filter house which provides air to the gas turbine combustion system, through dedicated filters. The axial fans are embedded in a ducting system which discharges fresh air inside the enclosure where the gas turbine is housed. As the operations of the gas turbine need to be guaranteed in the event of fan failure, a backup redundant system is located in a duct parallel to the main one. One of the main requirements of a ventilation fan is the reliability over the years as the gas turbine can be installed in remote areas or unmanned offshore platforms with limited accessibility for unplanned maintenance.
For such reasons, the robustness of the ventilation system and a proper understanding of coupling phenomena with the axial fan is a key aspect to be addressed when designing a gas-turbine system. Here a numerical study of a ventilation system carried out with RANS and LES based methodologies will be presented where the presence of the fan is synthetized by means of static pressure discontinuity. Different operations of the fans are investigated by means of RANS in order to compare the different operating points, corresponding to 1) clean and 2) dirty filters operations, 3) minimum and 4) maximum pressure at the discharge section. Large Eddy Simulations of the same duct were carried out in the maximum loading condition for the fan to investigate the unsteady response of the system and validate its correct arrangement.
All the simulations were carried out using OpenFOAM, a finite volume open source code for CFD analysis, treating the filters as a porous medium and the fan as a static pressure discontinuity according to the manufacturer’s characteristic curve. RANS modelling was based on the cubic k-ε model of Lien et al. while sub-grid scale modelling in LES was based on the 1 equation model of Davidson.
Computations highlighted that the ventilation system was able to work in similarity for flow rates between 15 m3/s and 23.2 m3/s and that the flow conditions onto the fan suggest that the aerodynamic stress on the device could be reduced introducing in the duct flow straighteners or inlet guided vanes.
Aeroacoustic Computational Analysis of a Steam Turbine Trip Valve
Authors: Bianchini C. , Da Soghe R. , Cosi L. , Imparato E. 
Published: August 2015

The continuously growing request for high operational flexibility and extreme customization also for large scale steam turbine creates new challenges in the design of steam machineries. Most components in fact need to be operated, and hence verified, in conditions far from those they were originally designed for. Constant upgrade of selection tools for the assembly of the engine is thus required to extend correlations applicability range for both averaged aerodynamic performance and unsteady effects of critical components. In this context a trip valve of a medium sized steam turbine was analyzed by means of CFD analysis. The investigation had two principal objectives: the estimate of aerodynamic losses within the valve and the evaluation of fluctuating loads effects.
For the time averaged behavior, first pressure losses across the strainer band were evaluated through a detailed simulation of the filter geometry in a simplified configuration to characterize an equivalent distributed momentum loss in the complete domain. Steady state solutions of the flow within the valve and the diffuser were then obtained for the entire range of operations to evaluate the global valve loss coefficient.
The unsteady steam behavior is predicted by means of the Scale Adaptive Simulation principle to evaluate major characteristic frequencies and verify fluctuations amplitudes on critical points.
Finally an acoustic propagation analysis is performed to estimate possible interactions between aerodynamic forcing and proper acoustic modes both verifying sufficient decoupling between aerodynamic and acoustic proper frequencies and analysing the forced acoustic response when subjected to registered pressure fluctuations.
Optimization of Tilting-Pad Journal Bearings for Integrally Geared Compressors
Authors: Havlik Nico , Lutz Michael 
Published: August 2015

Tilting-pad journal bearings (TPJBs) support highly loaded high speed rotors with high requirements on rotordynamic behavior. Typical applications therefore are integrally geared compressors, where the gear force of the high speed pinions (HSPs) is at least one magnitude higher than the gravity force.
A continuously rising demand for increasing the overall efficiency of integrally geared compressors leads to a necessity to expand TPJBs operation limits. Allowable limits of actual bearings often result in limitations for thermodynamical compressor design. In addition, bearings generate 20% to 40% of the mechanical power losses in integrally geared compressors. Improvements in the bearing design have to be performed in order to meet the challenges of rising loads and speeds.
This paper presents an optimization of TPJBs for integrally geared compressors to meet the further demand of higher operation limits.
Flowfield and Heat Transfer Numerical Analysis of a Stator Vane Endwall With High Freestream Turbulence
Authors: Andreini A. , Bianchini C. , Burberi E. , Facchini B. , Abram R. , Licata D. , Spataro G. 
Published: August 2015

Among the different parts subjected to hot gas flow, endwall heat transfer evaluation is particularly challenging because the flow is strongly affected by secondary effects. Large three-dimensional flow structures introduce remarkable spatial variation of heat transfer, both along streamwise and spanwise directions, making the use of simplified modelling approaches questionable in terms of reliability, and at the same time increasing the challenge for high fidelity computational methods.
The aim of the present contribution is to describe the work done in the assessment of computational methods for the estimate of high pressure vane endwall heat transfer for industrial applications. Efforts were first devoted to the development and validation of an accurate computational procedure against a large set of aerodynamic and heat transfer data, available from literature, for both airfoil and endwall of a low-pressure linear cascade with low and high inlet turbulence levels.
The analysis, focused on steady state computations, is principally devoted to the turbulence modelling assessment, including non-linear turbulence closure as well as transition modelling.
Obtained results showed that the aerodynamics of both passage and endwall are well captured independently of the turbulence modelling while a large impact on both pattern and averaged value is verified for the heat transfer.
Turbulent Scale Resolving Modelling of Rotating Stall in Low-Pressure Steam Turbines Operated Under Low Volume Flow Conditions
Authors: Megerle Benjamin , Rice Timothy Stephen , McBean Ivan , Ott Peter 
Published: August 2015

Non-synchronous excitation under low volume operation is a major risk to the mechanical integrity of last stage moving blades (LSMBs) in low-pressure (LP) steam turbines. These vibrations are often induced by a rotating aerodynamic instability similar to rotating stall in compressors.
Unsteady computational fluid dynamics (CFD) has been applied to simulate the rotating stall phenomenon in two model turbines. It is shown that the investigated flow field presents a challenge to conventional Reynolds-averaged Navier–Stokes equations simulations. The modelling has been enhanced by applying scale-resolving turbulence modelling, which can simulate large-scale turbulent fluctuations. With this type of simulation a qualitative and quantitative agreement between CFD and measurement for the unsteady and time averaged flow field has been achieved.
The results of the numerical investigation allow for a detailed insight into the dynamic flow field and reveal information on the nature of the excitation mechanism. It is concluded that the CFD approach developed can be used to assess LSMB blade designs prior to model turbine tests to check whether they are subjected to vibration under LVF caused by rotating stall.
A Fully Coupled Aero, Thermal, and Structural Lifetime Model for Root Cause Failure Analysis and Robust Redesign of an Industrial F Class Gas Turbine Blade
Authors: Houck Lonnie , Sewell DeAnna , Burke Megan , Vogel Gregory 
Published: August 2015

Modern large frame F, G, & J class gas turbine flow path component design requires the complex integration of multiple design disciplines that traditionally reside with distinct specialists. A traditional design system for an actively cooled gas turbine blade includes aerodynamicists, heat transfer engineers, structural engineers and a failure or lifetime prediction engineers passing information through a manual process with a small number of iterations between the disciplines. Design or manufacturing engineers can also be involved ensuring manufacturability and policing best practices in a predominantly deterministic design system. Over the past few decades robust design or probabilistic design philosophies along with cluster computing advancements have accelerated the release of commercial software that allows for the automation of multiple analytical evaluations at off design points. These software codes allow for process automation of several independent codes executed multiple times at various conditions for automated design of experiment (DOE), and reliability analysis using Monte Carlo or other advanced approximate probabilistic methods across the entire design system.
In this paper, the authors are presenting a novel approach of using a commercially available process integration tool to fully integrate a series of other commercially available tools for a root cause failure analysis of a F class turbine blade rather than a new make design. The analysis incorporated a computational fluid dynamics model (CFD) to define inlet temperatures and pressure profiles, a fully conjugate thermal analysis interacting with a finite element (FEA) solver linked to a proprietary creep lifetime prediction model. A DOE was executed to define the meaningful parameters and help rule out potential causes of failure such as loss of coating or compromised cooling system as a contributing factor of the failure which greatly reduced the amount of time and money needed for the investigation. A probabilistic failure analysis was then executed and surrogate models created for quick probabilistic assessment for different operating conditions. This allowed for validation against fleet history to explain the single engine failure not previously observed. Setting up the non-deterministic models initially allowed for rapid redesign in less than 1 month time with confidence that the true root cause was identified and mitigated. It further allowed for feedback and calibrations to the traditional design system methodology.