bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulations of Friction Damping on Laboratory-Test-Rigs of Rotors and Stators of an Axial Compressor
Authors: Miyakozawa Tomokazu , Peng Caetano , Andrews Stuart , Brace Mark , Schroeter Thomas , Rose Martin 
Published: August 2015

This paper presents comparisons of the non-linear behaviours and the damping characteristics of rotors and stators. It assesses the differences between the linear FE predicted modeshapes and the measured operating deflection shapes (ODS) of rotors and stators of an axial compressor. The comparisons are between the experimental results obtained from the laboratory rig damping tests and the numerical nonlinear forced response analyses. The damping tests are performed using an experimental rig apparatus driven by piezoelectric and electromagnetic shakers. The forced response analyses are performed on the finite element (FE) models that simulate the laboratory rig configurations using in-house multi-harmonic balance non-linear forced response code named FORSE.
Firstly, the measured resonant frequencies and ODS are compared against the predicted results. Moreover, some comparisons of the damping characteristics and local interactions at friction interfaces are discussed. Then, the FORSE predicted instantaneous displacements are examined to understand possible changes in ODS using the Modal Assurance Criterion (MAC) technique. It was found that the instantaneous displacements predicted by FORSE are significantly different from the modeshapes predicted by the linear FE tool. These results suggest that the experimentally measured ODS of the components may also differ from linear FE results. The predicted normalised maximum alternating stresses are also shown to be different from the standard linear FE results due to the modal coupling effects between the neighbouring modes. These findings should alert the engineers about the possibilities of misinterpreting component vibration responses due to the changes in ODS.
CFD Investigation of Brush Seal Leakage Performance Depending on Geometric Dimensions and Operating Conditions
Authors: Doğu Yahya , Sertçakan Mustafa C. , Bahar Ahmet S. , Pişkin Altuğ , Arıcan Ercan , Kocagül Mustafa 
Published: August 2015

Brush seals require custom design and tailoring due to their behavior driven by flow dynamic, which has many interacting design parameters, as well as their location in challenging regions of turbomachinery. Therefore, brush seal technology has not reached a conventional level across the board standard. However, brush seal geometry generally has a somewhat consistent form. Since this consistent form does exist, knowledge of the leakage performance of brush seals depending on specific geometric dimensions and operating conditions is critical and predictable information in the design phase. However, even though there are common facts for some geometric dimensions available to designers, open literature has inadequate quantified information about the effect of brush seal geometric dimensions on leakage.
This paper presents a detailed CFD investigation quantifying the leakage values for some geometric variables of common brush seal forms functioning in some operating conditions. Analyzed parameters are grouped as follows; axial dimensions, radial dimensions and operating conditions.
The axial dimensions and their ranges are front plate thickness (z1=0.040–0.150in.), distance between front plate and bristle pack (z2=0.010–0.050in.), bristle pack thickness (z3=0.020–0.100in.), and backing plate thickness (z4=0.040–0.150in.).
The radial dimensions are backing plate fence height (r1=0.020–0.100in.), front plate fence height (r2=0.060–0.400in.), and bristle free height (r3=0.300–0.500in.).
The operating conditions are chosen as clearance (r0=0.000–0.020in.), pressure ratio (Rp=1.5–3.5), and rotor speed (n=0–40krpm).
CFD analysis was carried out by employing compressible turbulent flow in 2-D axi-symmetric coordinate system. The bristle pack was treated as a porous medium for which flow resistance coefficients were calibrated by using literature based test data.
Selected dimensional and operational parameters for a common brush seal form were investigated, and their effects on leakage performance were quantified. CFD results show that, in terms of leakage, the dominant geometric dimensions were found to be the bristle pack thickness and the backing plate fence height. It is also clear that physical clearance dominates leakage performance, when compared to the effects of other geometric dimensions. The effects of other parameters on brush seal leakage were also analyzed in a comparative manner.
Analysis of Bifurcations in Multiharmonic Analysis of Nonlinear Forced Vibrations of Gas-Turbine Engine Structures With Friction and Gaps
Authors: Petrov E. P. 
Published: August 2015

An efficient frequency-domain method has been developed to analyse the forced response of large-scale nonlinear gas-turbine structures with bifurcations. The method allows: detection and localization of the design and operating conditions sets where bifurcations occur; calculation of tangents to the solution trajectory and continuation of solutions under parameter variation for structures with bifurcations.
The method is aimed at calculation of steady-state periodic solution and multiharmonic representation of the variation of displacements in time is used. The possibility of bifurcations in realistic gas-turbine structures with friction contacts and with cubic nonlinearity has been shown.
Investigation of Flow Aerodynamics for Optimal Fuel Placement and Mixing in the Radial Swirler Slot of a Dry Low Emission Gas Turbine Combustion Chamber
Authors: Agbonzikilo Festus Eghe , Owen Ieuan , Sadasivuni Suresh Kumar , Bickerton Ronald A. 
Published: August 2015

This paper presents the results of a detailed investigation of the fuel-air mixing processes that take place within the radial swirler slot of a dry low emission combustion system. The aerodynamics of the flow within the slot is complex and this, together with the placement of the fuel holes with cross injection, controls the mixing of the fuel and air. Computational fluid dynamics (CFD) with the Shear Stress Transport (k-ω) turbulence model was used for flow and mixing predictions within the radial swirler slot and for conducting a CFD-based Design of Experiments (DOE) optimisation study, in which different parameters related to the fuel injection holes were varied. The optimisation study was comprised of 25 orthogonal design configurations in a Taguchi L25 orthogonal array. The test domain for the CFD, and its experimental validation, was a large-scale representation of a swirler slot from a Siemens proprietary DLE combustion system. The DOE study showed that the number of fuel holes, injection hole diameter and inter-hole distance are the most influential parameters for determining optimal fuel mixing.
Consequently, the optimised mixing configuration obtained from the above study was experimentally tested on an atmospheric test facility. The mixing patterns from experiments at various axial locations across the slot are in good agreement with the mixing predictions from the optimal CFD model. The optimised fuel injection design improved mixing compared with the original design by about 60%.
Thrust Measurement Model-Based Correction System for Turbine Engine Test Cell Dynamic Data
Authors: Palmer Carl , Hettler Eric 
Published: August 2015

This paper describes a turbine engine thrust estimator that computes “virtual measurements” of dynamic engine thrust and other parameters of interest from test cell data in a very short amount of time. The system ‘tunes’ a user’s engine model, as developed in the commonly used Numerical Propulsion System Simulation (NPSS), by optimizing system biases and health parameters to match the sensor outputs of a set of steady state data points across the operating range. The tuned model is then used to create a constant gain extended Kalman filter that is added directly within the NPSS model code. The results, including thrust, from this NPSS model with Kalman filter are then presented as the ‘actual’ corrected data.
Key aspects of the system include:
• Utilization of and tight integration with NPSS. This ensures that the results always preserve mass and energy, and are realistic from an engine performance point of view.
• Flexibility; any NPSS model for any gas turbine engine can be used.
• The ability for the whole tuning process to ‘correct’ not just noisy test data, but also performance parameters within the user’s actual NPSS model.
• A GUI that leads the user through each step of the process, such as matching NPSS variable names to signals in the actual test cell data files, and selection of ‘tuners’ (performance parameters, sensor errors) and Kalman filter variables.
The system has been tested both on a simulated two spool turbojet engine, plus an actual two spool turbojet engine, with recorded test cell data.
Low Cycle Fatigue Model Selection by Performance Analysis
Authors: Riva Andrea , Vacchieri Erica , Poggio Eleonora , Merckling Gunther 
Published: August 2015

A reliable low cycle fatigue (LCF) model requires the selection of appropriate damage mechanism components necessary to accurately approximate experimental life data. In particular, two fundamental tasks have to be performed: firstly, identify the most appropriate model among those available in literature, and secondly, verify that the model is appropriate in relation to the operational conditions of the component whose life is under evaluation (e.g., check if the model accounts for all the relevant damage mechanisms and phenomena).
The European Creep Collaborative Committee (ECCC) developed a procedure that supports the researcher in evaluating performances and reliability of creep models, known as Post Assessment Tests (PATs). At the moment, there is no equivalent procedure for low cycle fatigue and ECCC work may provide the LCF researcher with useful guidelines.
This paper is intended to investigate, compare and suggest which kind of verification is appropriate to identify any possible misbehavior in a fatigue model or in the LCF tests that supported the model. This procedure involves an analysis of the model performances in terms of comparison with the experimental population, supported by a deep knowledge of the damage mechanisms of the given material. Particular attention will be paid to materials with a particularly high dispersion, such as cast nickel-based superalloys.
This paper is also meant to stimulate the fatigue data user community to propose and share methodologies in the perspective of the creation of a recommendation code, similar to what has been done by ECCC for creep.
Experimental and Numerical Investigation of Labyrinth Seal Clearance Impact on Centrifugal Impeller Performance
Authors: Marechale Russell , Ji Min , Cave Michael 
Published: August 2015

Labyrinth seals are widely used in industrial multistage centrifugal compressors to reduce internal leakage and maintain compressor performance for a prolonged operation time. The leakage flow across the shroud seal of covered impellers and the hub seal of the rotating shaft has an important effect on the compressor performance. The amount of leakage flow is primarily a function of seal running clearances, which is typically designed based on the compressor working environment, such as pressure and temperature conditions. The present paper discusses the experimental and numerical studies of seal clearance impact on the performance and operation of a single stage centrifugal compressor.
Two experimental campaigns of running a medium-flow coefficient impeller and a low-flow coefficient impeller with various radial clearances of the impeller shroud and the hub labyrinth seal were conducted based on the configuration of the impeller and the return channel system in a closed-loop compressor test rig. The experimental investigation consists of both the overall stage performance test and the traverse test of the flow field downstream of the impeller using three-hole Cobra probes. Static pressure taps were arranged in the impeller shroud cavity in order to obtain the stream-wise pressure distribution. CFD simulations were then performed to compare with the test results. The paper presents the analysis of test data and simulation results of five arrangements of the impeller shroud and the hub seal radial clearances. The impacts of seal clearance height on stage efficiency and head are quantitatively evaluated. The impact on impeller internal flow field and cavity pressure distributions and swirl angle are discussed.
Findings from this study are that efficiency reduction with increased seal clearance was as expected, but impeller Euler work was significantly reduced. CFD simulation was validated as a tool for predicting these effects and provides some understanding of the flow mechanisms.
LES Simulation of an Enclosed Turbulent Reacting Methane Jet With the Tabulated Premixed CMC Method
Authors: Velez Carlos , Martin Scott , Jemcov Aleksander , Vasu Subith 
Published: August 2015

The Tabulated Premixed Conditional Moment Closure Method (T-PCMC) has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes in a RANS environment [1]. Here the premixed conditional moment closure method is extended to Large Eddy Simulation. The new model is validated with the turbulent, enclosed reacting methane backward facing step data from El Banhawy [2]. The experimental data has a rectangular test section at atmospheric pressure and temperature with an inlet velocity of 10.5 m/s and an equivalence ratio of 0.9 for two different step heights. Contours of major species, velocity and temperature are provided.
The T-PCMC model falls into the class of table lookup turbulent combustion models where the combustion model is solved offline over a range of conditions and stored in a table that is accessed by the CFD code using three controlling variables; the reaction progress variable, variance and local scalar dissipation rate. The local scalar dissipation is used to account for the affects of the small scale mixing on the reaction rates. A presumed shape beta function PDF is used to account for the effects of large scale turbulence on the reactions. Sub-grid scale models are incorporated for the scalar dissipation and variance. The open source CFD code OpenFOAM is used with the compressible Smagorinsky LES model. Velocity, temperature and major species are compared to the experimental data. Once validated, this “low runtime” CFD turbulent combustion model will have great utility for designing the next generation of lean premixed gas turbine combustors.
Preliminary Design Assessments of Pusher Geared Counter-Rotating Open Rotors: Part I — Low Pressure System Design Choices, Engine Preliminary Design Philosophy and Modelling Methodology
Authors: Bellocq Pablo , Garmendia Iñaki , Sethi Vishal 
Published: August 2015

In this 2-part publication, the impact of the main low pressure system parameters of a pusher counter rotating Geared Open Rotor (GOR) on mission fuel burn, certification noise and emissions is presented for a 160 PAX medium haul class aircraft.
Due to their high propulsive efficiency, GORs have the potential to significantly reduce fuel consumption and emissions relative to conventional high bypass ratio turbofans. However, this novel engine architecture presents many design and operational challenges both at engine and aircraft level.
The assessment of the impact of the main low pressure preliminary design parameters of GORs on mission fuel burn, certification noise and emissions is necessary at preliminary design stages in order to identify optimum design regions. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational or regulatory constraints.
Part I of this two-part publication describes the main low pressure (LP) system design choices for a GOR as well as the preliminary design philosophy and simulation framework developed for the assessments. Part II presents the assessment studies. The simulation framework described in this paper comprises the following models: engine and aircraft performance, engine mechanical design and weight, engine certification noise and emissions.
A novel aspect of the presented simulation framework is that the design point efficiency and the design feasibility of the low pressure components are calculated for each engine design.
A General Model for Two-Point Contact Dry-Friction Whip and Whirl: Further Advancements and Experimental Test Results
Authors: Wilkes Jason C. , Allison Tim 
Published: August 2015

Numerous papers have investigated the behavior of dry-friction whip and whirl; most of them consider contact between a rotor and stator at a single location. For rotors running on multiple magnetic bearings, air bearings, or bushings, equipment failure may result in rub at more than one location. For these cases, it is important to have an analytical model that characterizes possible regions of two-point contact dry-friction whip and whirl.
The current work presents a general model to predict possible whirl regions for multi-contact dry-friction whip and whirl, allowing for an arbitrary phase between contact locations. In theory this method can be applied to more than two contact locations; however, a two-point contact example case is developed and compared to results from an experimental test rig developed to demonstrate multi-contact dry-friction whip and whirl in the current work.
An Investigation on the Effect of Creep Shakedown on the Creep Behavior of an Industrial Gas Turbine Blade
Authors: Zhao Jun , Koul Ashok K. , Banerjee Avisekh 
Published: August 2015

The creep life computation of gas turbine hot section components using any damage modeling technique requires typical inputs of stress and temperature under actual engine operating conditions. The magnitude of these inputs is governed by the static or dynamic transient loading conditions that a component may be subjected to during service. The long term creep damage accumulation process in a hot section component leads to strain accumulation in the component with time. The rate of change of this strain accumulation in different regions of a component is controlled by the magnitude of the local stress, stress gradient and temperature. In some regions, the creep damage accumulation process may lead to a substantial change in the local stress distribution, also called the “Creep Shakedown”, and this time-dependent stress redistribution can have a substantial impact on the component creep life.
The creep shakedown based creep life analysis of a GE Frame 7EA first stage turbine blade under off-design base-load engine operating conditions is studied. The evolution of the stress and strain in different regions of the blade with service time was analyzed using the finite element method. A user defined Garofalo model with hyperbolic sine creep rule was incorporated in the finite element analysis (FEA). The creep shakedown in the component is demonstrated to cause a local time-dependent stress redistribution effect in the FEA simulation. The significant stress variation and creep strain accumulation was observed in the creep critical regions where local stress raisers were present and/or a high temperature gradient due to internal cooling design existed. These effects are discussed in detail from a materials engineering perspective.
System Integration and Techno-Economy Analysis of the IGCC Plant With CO2 Capture: Results of the EU H2-IGCC Project
Authors: Mansouri Majoumerd Mohammad , Assadi Mohsen , Breuhaus Peter , Arild Øystein 
Published: August 2015

The overall goal of the European co-financed H2-IGCC project was to provide and demonstrate technical solutions for highly efficient and reliable gas turbine technology in the next generation of integrated gasification combined cycle (IGCC) power plants with CO2 capture suitable for combusting undiluted H2-rich syngas.
This paper aims at providing an overview of the main activities performed in the system analysis working group of the H2-IGCC project. These activities included the modeling and integration of different plant components to establish a baseline IGCC configuration, adjustments and modifications of the baseline configuration to reach the selected IGCC configuration, performance analysis of the selected plant, performing techno-economic assessments and finally benchmarking with competing fossil-based power technologies.
In this regard, an extensive literature survey was performed, validated models (components and sub-systems) were used, and inputs from industrial partners were incorporated into the models. Accordingly, different plant components have been integrated considering the practical operation of the plant. Moreover, realistic assumptions have been made to reach realistic techno-economic evaluations.
The presented results show that the efficiency of the IGCC plant with CO2 capture is 35.7% (lower heating value basis). The results also confirm that the efficiency is reduced by 11.3 percentage points due to the deployment of CO2 capture in the IGCC plant. The specific capital costs for the IGCC plant with capture are estimated to be 2,901 €/(kW net) and the cost of electricity for such a plant is 90 €/MWh.
It is also shown that the natural gas combined cycle without CO2 capture requires the lowest capital investment, while the lowest cost of electricity is related to IGCC plant without CO2 capture.
Recent Research Progress on Supercritical Carbon Dioxide Power Cycle in China
Authors: Wang Junfeng , Huang Yanping , Zang Jinguang , Liu Guangxu 
Published: August 2015

China has started the investigations on supercritical carbon dioxide (S-CO2) power cycle since 2011. The aim of this project is to understand the feasibility and economics of coupling S-CO2 power cycle with Chinese Gen IV nuclear reactors. Up to now, the pre-concept design and feasibility evaluation has been accomplished. The focus in the next step is fundamental research on thermal-hydraulics and materials and Integral Test Loop design, construction, and operation.
Nuclear Power Institute of China (NPIC) has been a leader in S-CO2 power cycle development in China. With contractors and collaborators from China and UK, NPIC has constructed a natural circulation test loop and started the Integral Test Loop design. In this paper, an overview of the progress on S-CO2 power cycle development in NPIC is provided. The testing results from a small-scaled natural circulation test loop, the CFD code verification and validation, and the considerations and design features of Integral Test Loop will be summarized.