bluuebunny/crossref_metadata_2025_split huggingface dataset:
3-D Computational Loss Analysis of an Asymmetric Volute Twin-Scroll Turbocharger
Authors: Palenschat Torsten , Newton Peter , Martinez-Botas Ricardo F. , Müller Markus , Leweux Johannes 
Published: August 2017

In times of stringent emission standards for automotive and truck applications, exhaust gas recirculation (EGR) is used in IC engines to reduce NOx emissions by recirculating a portion of an engine’s exhaust gas. The amount of exhaust gas determined for EGR is withdrawn from the exhaust gas route and routed back into the combustion chamber. The recirculated exhaust gas acts as an inert gas and, when mixed with the pre-combustion mixture, helps to decrease the combustion temperature and thus NOx emissions.
Designed for a diesel engine within a truck application, the turbine in this particular research project is fed by two cylinder groups, however, only the exhaust gas of one group is recirculated. The reduced mass flow in the small turbine scroll (EGR-scroll) through EGR withdrawal, along with the increased pressure required for EGR transport, leads to a massive reduction in the mass flow parameter of the EGR-scroll.
The common turbocharger design process has been based on steady admission rather than unsteady admission given through the pulsating nature of multi-cylinder admission. This has lead to diverging results of turbochargers performing well on steady hot gas test rigs compared to performing badly in the final tests on the engine itself.
In this paper however, unequal admission resulting from pulsating admission is taken into account. Based on unsteady admission, a methodology is proposed for steady computations with unequal admissions, and a thorough 3D CFD loss analysis is to be presented to understand the turbine behaviour, reveal the regions for improvements, and provide a framework for further development.
Reduction of Soot Emitted by Gas Turbines Fired on Gasoil
Authors: Galantine Bernard , Lepante Philippe , Angebert Alex , Vierling Matthieu , Aboujaib Maher , Sokolov Dmitry , Plouhinec Mickael , Moliere Michel 
Published: August 2017

Particulate matter (PM) emitted by the combustion of liquid fuels consist of both ash and soot particles. For installations fired on heavy fuel oil, ash particles represent a substantial fraction of the PM emitted. However, when one burns distillate oil, soot accounts for more than 95% of the PM emission. There is currently a marked move towards the reduction of particles emitted by combustion installations. This includes gas turbines operated in cogeneration or in simple/combined cycle. This trend is driven namely by the EU BREF (Best Available Techniques Reference Document) and IED (Industrial Emission Directive), which recommend more stringent PM limitations for the combustion of gaseous and liquid fuels. Due to the proposed regulations GE has performed testing to evaluate the efficiency of catalysts mobilized in the form of fuel additives on soot emissions of heavy duty gas turbines (“GT”) fired on # 2 diesel oil (#2 DO) also known as gasoil.
In the framework of a collaboration between EDF and GE, a full-scale test has been performed at the Jarry Sud power plant in Guadeloupe (West Indies), involving a Frame 6B, with three types of benign oxidation catalyst additives: cerium (IV), cerium (III) and iron (III). The results of this trial proved successful with a PM abatement level up to 80% attained at full load.
The paper summarizes the preparation and execution of this field test with emphasis placed on the activity of cerium that appeared efficient at concentrations as low as a few ppm. The performances of iron and cerium are also compared.
A Review of the Experience Achieved at the Yugadanavi 300 MW CCGT in Sri Lanka: Increasing the Firing Temperature of Gas Turbines Using a Novel Vanadium Inhibitor
Authors: Marikkar Nuhuman , Jayath Tharindu , Egodawatta Kithsiri , Vierling Matthieu , Aboujaib Maher , Sokolov Dmitry , Meskers Donald , Russell Robert , Moliere Michel 
Published: August 2017

In regions developing rapidly but deprived of natural gas, gas turbines (GT) in combined cycles (CC) fired on Heavy Fuel Oil (HFO) can represent effective and environmentally viable power generation options.
The 300 MW Yugadanavi plant in Sri Lanka, which features two 9E GTs burning low-sulfur HFO, best exemplifies this specific situation. This project was fast-tracked in 2006, when the country started its fast development and the national grid needed fast power additions and frequency stability. Since 2008, it has been supplying 200 MWe to the Ceylonese grid, in simple cycle. Then in 2010, its capacity rose up to 300 MWe without any extra fuel consumption, after its conversion to a combined cycle.
In November 2016, Yugadanavi has completed 55,000 hours of successful operation, has generated 6,000 TWh and burned 1 million tons of HFO achieving on average efficiency and reliability performances as high as 44% and 96% respectively.
Starting 2010, LTL and GE joined their efforts in plant upgrade initiatives. In 2014 they demonstrated an efficient method to reduce the smoke emissions, using benign combustion catalysts. Within a next upgrade step, a new vanadium inhibition technology has been field-tested in 2015–2016, which enables improving the availability and energy performances of the plant by namely increasing the firing temperature of the gas turbines.
After recalling the key milestones of this significant HFO project, the joint paper will outline the operation experience and positive environmental outcomes of the developments carried out within an LTL-GE collaboration, with a special emphasis on the most recent results obtained with the new inhibition technology.
A Parametrization Describing Blisk Airfoil Variations Referring to Modal Analysis
Authors: Backhaus Thomas , Maywald Thomas , Schrape Sven , Voigt Matthias , Mailach Ronald 
Published: August 2017

This paper will present a way to capture the geometric blade by blade variations of a milled from solid blisk as well as the manufacturing scatter. Within this idea it is an essential task to digitize the relevant airfoil surface as good as possible to create a valid surface mesh as the base of the upcoming evaluation tasks. Since those huge surface meshes are not easy to handle and are even worse in getting quantified and easy interpretable results, it should be aimed for an easily accessible way of presenting the geometric variation.
The presented idea uses a section based airfoil parametrization that is based on an extended NACA-airfoil structure to ensure the capturing of all occurring characteristic geometry variations. This Paper will show how this adapted parametrization method is suitable to outline all the geometric blade by blade variation and even more, refer those airfoil design parameters to modal analysis results such as the natural frequencies of the main mode shapes. This way, the dependencies between the modal and airfoil parameters will be proven.
Evaluation of Property Methods for Modeling Direct-Supercritical CO2 Power Cycles
Authors: White Charles W. , Weiland Nathan T. 
Published: August 2017

Direct supercritical CO2 (sCO2) power cycles have received considerable attention in recent years as an efficient and potentially cost-effective method of capturing CO2 from fossil-fueled power plants. These cycles combust natural gas or syngas with oxygen in a high pressure (200–300 bar), heavily-diluted sCO2 environment, such that the fluid entering the turbine is 90–95% CO2, with the balance composed primarily of H2O, CO, O2, N2 and Ar. After recuperation of the turbine exhaust thermal energy, water is condensed from the cycle, and the remainder is recompressed for either return to the combustor or for enhanced oil recovery (EOR) or storage. The compression power requirements vary significantly, depending on the proximity of the operating conditions to the CO2 critical point (31 °C, 73.7 bar), as well as to the level of working fluid dilution by minor components. As this has a large impact on cycle and plant thermal efficiency, it is crucial to correctly capture the appropriate thermo-physical properties of these sCO2 mixtures when carrying out performance simulations of direct sCO2 power plants. These properties are also important to determining how water is removed from the cycle, and for accurate modeling of the heat exchange within the recuperator.
This paper presents a quantitative evaluation of ten different property methods that can be used for modeling direct sCO2 cycles in Aspen Plus®. REFPROP is used as the de facto standard for analyzing indirect sCO2 systems, where the closed nature of the cycle leads to a high purity CO2 working fluid. The addition of impurities due to the open nature of the direct-sCO2 cycle, however, introduces uncertainty to the REFPROP predictions. There is a limited set of mixtures available for which REFPROP can be reliably used and there are a number of species present in a coal-fired direct-fired sCO2 cycle that REFPROP cannot accommodate. Even with a relatively simplified system in which the trace components are eliminated, simulations made using REFPROP require computation times that often preclude its use in parametric studies of these cycles. Consequently, a series of comparative analyses were performed to identify the best physical property method for use in Aspen Plus® for direct-fired sCO2 cycles. These property methods are assessed against several mixture property measurements, and offer a relative comparison to the accuracy obtained with REFPROP. This study also underscores the necessity of accurate property modeling, where cycle performance predictions are shown to vary significantly with the selection of the physical property method.
Investigation of Loss Impact From Production-Like Features in a Compressor Duct Under Engine Realistic Conditions
Authors: Wallin Fredrik , Ross Mark H. , Rusche Max , Morris Scott , Ray Steven 
Published: August 2017

An experimental and numerical investigation of the flow in a compressor duct with engine-realistic in-production features is presented in this paper. The experimental testing was conducted in the ND-FSCC test facility at University of Notre Dame, Indiana, USA. A baseline duct was also tested for back-to-back comparison.
The ducts were heavily instrumented; duct inlet and exit flowfields were scanned using a five-hole pressure probe that provided total pressure, velocities and flow angles. Based on the five-hole probe total pressures, duct losses could be assessed. Furthermore the duct inlet boundary layers were traversed and turbulence intensity levels were assessed. For the CFD analysis of the production-like duct, a highly complex computational grid, resolving all the geometrical features present, was used. A previously validated surface roughness model was used to account for the cast aero-surfaces.
Both experimental and numerical results show that there is a significant increase in loss for the production-like duct when compared to the baseline duct loss. The CFD results agree very well with experimental results for the baseline duct, which makes it possible to use the experimental data recorded for the production-like duct to validate CFD tools for real geometry effects, such as interface steps and surface roughness for example.
Large Eddy Simulation of Transitional Flow in a Compressor Cascade
Authors: Rizvi Syed Anjum Haider , Mathew Joseph 
Published: August 2017

At off-design conditions, when the blade Reynolds number is low, a significant part of the blade boundary layer can be transitional. Then, standard RANS models are unable to predict the flows correctly but explicit transition modeling provides some improvement. Since large eddy simulations (LES) are improvements on RANS, the performance of LES was examined by simulating a flow through a linear, compressor cascade for which experimental data are available — specifically at the Reynolds number of 210,000 based on blade chord when transition processes occur over a significant extent of the suction surface.
The LES were performed with an explicit filtering approach, applying a low-pass filter to achieve sub-grid-scale modeling. Explicit 8th-order difference formulas were used to obtain high resolution spatial derivative terms. An O-grid was wrapped around the blade with suitable clustering for the boundary layer and regions of large changes along the blade. Turbulent in-flow was provided from a precursor simulation of homogeneous, isotropic turbulence. Two LES and a DNS were performed. The second LES refines the grid in the vicinity of the separation bubble on the suction surface, and along the span. Surface pressure distributions from all simulations agree closely with experiment, thus providing a much better prediction than even transition-sensitive RANS computations. Wall normal profiles of axial velocity and fluctuations also agree closely with experiment. Differences between LES and DNS are small, but the refined grid LES is closer to the DNS almost everywhere. This monotonic convergence, expected of the LES method used, demonstrates its reliability.
The pressure surface undergoes transition almost immediately downstream of the leading edge. On the suction surface there are streaks as expected for freestream-turbulence-induced transition, but spots do not appear. Instead, a separating shear layer rolls up and breaks down to turbulence at re-attachment. Both LES capture this process. Skin friction distribution reveals the transition near the re-attachment to occur over an extended region, and subsequent relaxation is slower in the LES. The narrower transition zone in the DNS is indicative of the essential role of smaller scales during transition that should not be neglected in LES. Simulation data also reveal that an assumption of laminar kinetic energy transition models that Reynolds shear stress remains small in the pre-transitional region is supported. The remaining differences in the predictions of such models is thus likely to be the separation-induced transition which preempts the spot formation.
Investigation Into the Thermal Limitations of Steam Turbines During Start-Up Operation
Authors: Topel Monika , Laumert Björn , Nilsson Åsa , Jöcker Markus 
Published: August 2017

Liberalized electricity market conditions and concentrating solar power technologies call for increased power plant operational flexibility. Concerning the steam turbine component, one key aspect of its flexibility is the capability for fast starts. In current practice, turbine start-up limitations are set by consideration of thermal stress and low cycle fatigue. However, the pursuit of faster starts raises the question whether other thermal phenomena can become a limiting factor to the start-up process. Differential expansion is one of such thermal properties, especially since the design of axial clearances is not included as part of start-up schedule design and because its measurement during operation is often limited or not a possibility at all.
The aim of this work is to understand differential expansion behavior with respect to transient operation and to quantify the effect that such operation would have in the design and operation of axial clearances. This was accomplished through the use of a validated thermo-mechanical model that was used to compare differential expansion behavior for different operating conditions of the machine. These comparisons showed that faster starts do not necessarily imply that wider axial clearances are needed, which means that the thermal flexibility of the studied turbine is not limited by differential expansion. However, for particular locations it was also obtained that axial rubbing can indeed become a limiting factor in direct relation to start-up operation. The resulting approach presented in this work serves to avoid over-conservative limitations in both design and operation concerning axial clearances.
Demonstration of a Dynamic Clearance Seal in a Rotating Test Facility
Authors: Messenger Andrew , Williams Richard , Ingram Grant , Hogg Simon , Tibos Stacie , Seaton Jon , Charnley Bernard 
Published: August 2017

The successful demonstration of the “Aerostatic Seal” in a half scale rotating facility is described in this paper. The Aerostatic seal is a novel dynamic clearance seal specifically designed for steam turbine secondary gas path applications. The seal responds to radial rotor excursions, so a reduced clearance can be maintained compared to conventional labyrinth seal without damage to the seal. This enables increased turbine performance through reduced leakage and increased tolerance of turbine transient events typically found during start up. The seal is an extension of the existing retractable seal design already deployed in commercial steam turbines.
The seal was tested in the Durham Rotating Seals Rig, which was developed specifically to test this device. The rig featured a rotor designed to run with large eccentricities to model high speed radial rotor excursions, and the seal was instrumented to measure the real time seal response to the rotor.
The experimental campaign has conclusively demonstrated the ability of the seal to dynamically respond to the rotor position. The key result is that the seal is able to track the rotor position at high speed, and hence maintain a mean seal clearance that is lower than the rotor eccentricity. Overall this work marks a key milestone in the development of the Aerostatic Seal, and leads the way to testing in a steam environment and application in steam turbine plant.
Seedgas Investigation of Turbine Stage and Seal Performance at Varying Cavity Purge Rates and Operating Speeds
Authors: Dahlqvist Johan , Fridh Jens 
Published: August 2017

The topic of hub cavity purge is investigated in a high-pressure axial low-reaction turbine stage. Both the sealing ability of the purge flow and the performance impact associated with its injection into the main flow are studied. Three operating speeds are investigated, namely a high loading case, the peak efficiency, and a high speed case, and purge flow rates across a wide range. The operating points coincide with investigations previously reported, where the flow field and stage efficiency was quantified using pneumatic probes. Comparative measurements are also performed, varying a leakage flow through the rotor below the hub platform.
The purge flow is now seeded with CO2 in order to measure its distribution throughout the stage, as it is injected into the wheelspace upstream of the rotor, allowing for quantification of the sealing effectiveness. This is done at a number of defined locations along the stator-side wall in the wheel space, resolving the radial variation through the cavity. Important radial variations of effectiveness are observed, confirming that the flow is in the regime of merged boundary layers, due to the narrow cavity, as compared to typical gas turbine operation with separated boundary layers. The trends are found to be related to operating speed and platform leakage.
With known sealing effectiveness, industry correlations may be adapted to make use of the variation of necessary purge rate to obtain a certain degree of sealing at a given operating point, and thereby optimize the efficiency.
In addition to quantification of potential hot-gas ingestion, the paper initiates an investigation of the transport of the purge flow in the main annulus, through sampling on the hub, as well as area traverse downstream of the rotor. The amount of sealing gas leads to opportunity to quantify the cooling performance of the purge flow in the main annulus. Both the cooling performance in the main annulus and cavity are shown to be significantly influenced by the rotor leakage, while its effect on efficiency is minor.
Thermomechanical Component Mode Synthesis for Blade Casing Interaction Prediction
Authors: Guerin Nicolas , Thouverez Fabrice , Gibert Claude , Legrand Mathias , Almeida Patricio 
Published: August 2017

Increasing the efficiency of turbomachines is a major concern as it directly translates into lower environmental impact and improved operational costs. One solution is to reduce the blade-casing operating clearance in order to mitigate aerodynamic losses at the unavoidable cost of increased structural unilateral contact and friction occurrences. In centrifugal compressors, the dynamic behaviour of the structures interacting through unilateral contact and friction is not yet fully understood. In fact, the heat generated during such events may affect the dynamics through thermal stresses.
This paper presents a complete thermomechanical modelling strategy of impeller rotor and casing, and of blade-tip/casing contact events. A fully coupled thermomechanical modal synthesis technique is introduced and applied to turbomachinery-related models. The blisk is reduced via a hybrid modal synthesis technique combining the Craig-Bampton method and the characteristic constraint mode method. The casing model is reduced using an axisymmetric harmonic modal synthesis. Both strategies involve thermomechanical modes embedding thermal dilatation effects. The contact modelling algorithm is then introduced. It handles unilateral contact and friction occurrences together with heating effects. This algorithm uses the above mentioned reduced-order models as input data to avoid CPU-intensive simulations.
The results show that the thermomechanical behaviour of the structures is well preserved by the reduction strategy proposed. Contact simulations on simple cases show qualitative results in accordance with expectations.
Further work is needed in order to validate the strategy based on experimental results. However, this methodology opens the way to extended multiphysics simulations of contact events in turbomachinery.
Pulsations in Gas Turbine Operation: Identification and Modeling With the Purpose of Online Engine Monitoring and Optimization
Authors: Weidner Frank S. , Lipperheide Moritz , Wirsum Manfred C. , Bernero Stefano , Gassner Martin 
Published: August 2017

Lean premixed combustion has become state of the art technology in gas turbines for power generation because of its very low emission potential in the context of tightening pollutant emissions regulations. Lean premixed combustion is yet also prone to combustion instabilities, resulting in thermo-acoustically induced acoustic pressure oscillations (pulsations). Understanding pulsation behavior over an enginés lifetime is of interest to accurately monitor the engine status, as wear and degradation typically affect combustion behavior and result in changes of both pulsations and emissions. Such improved understanding can be exploited for optimizing both the engine operation concept and the design of relevant hardware parts. In return, pulsation and hardware optimization may lead to reduced degradation and thus inherently more robust long-term operational behavior.
The study presented here is conducted for one specific gas turbine of GE’s GT24/GT26 fleet with sequential annular combustion. Based on operational data of the examined gas turbine, a semi-empirical modeling approach is introduced to describe the pulsations measured in the first (EV) combustion chamber. The target is to reproduce measured pulsation amplitudes as well as their different behaviors with engine load. The modeling presented here has been focused on pulsations in a distinctive frequency range below 1kHz. A model based on a small set of data obtained from initial commissioning is able to represent the pulsation behavior within a normalized root mean square error of 11%. Validation with long-term engine data shows that predicted pulsation levels are reasonably matching the initial operation period but increasingly deviate with engine operating time. By using additional data from later engine commissioning and adjustments, the robustness of the model is sensibly increased. Model accuracy on the training dataset remains similar at around 11%, but validation on the long-term data shows a significant decrease of the normalized root mean square error from over 21% to below 16%. Additional model improvements to further reduce prediction errors on long-term data have been also identified.