bluuebunny/crossref_metadata_2025_split huggingface dataset:
Partially Vaned Diffuser With Variable Cross-Section for Centrifugal Fans
Authors: Fischer Tore , Burgmann Sebastian , Rudersdorf Manuel , Seume Joerg R. 
Published: August 2017

The present research focuses on the efficiency improvement at part-load of a centrifugal fan for a 30 kW fuel cell combined heat and power (CHP) unit. For this purpose, the fan stage is equipped with a partially vaned diffuser with a variable cross-sectional area using a moving backplate.
The design and the performance of the partially vaned diffuser with a variable cross-sectional area are described in the first part of this paper. The performance results are compared to measurements of the same centrifugal fan with a vaneless diffuser carried out for the previous investigation. For the second part, the influence of the variable cross-sectional area on the diffuser flow field is investigated using optical PIV (Particle Image Velocimetry) measurements and CFD (Computational Fluid Dynamics) simulations.
The combination of a variable cross-section, partially vaned diffuser was able to achieve a 10 percent increase in pressure ratio, a 5 percentage points increase in part-load efficiency while maintaining the whole operating range of the vaneless, constant cross section reference design.
Experimental Optimization of Rolls-Royce AE3007 Sump Design
Authors: Chandra Budi W. , Collicott Steven H. , Munson John H. 
Published: August 2017

The original sump design of Rolls-Royce AE3007 central sump is a tangential sump. An experimental program at Purdue University was conducted to investigate the characteristics of a tangential sump design. The research employed a bespoke experimental rig consisting of modular transparent chamber to allow unprecedented view of the two-phase flow inside the bearing chamber. It was found that a persistent liquid pooling near the drain entrance of a tangential sump obstructs the outflow to the scavenge off-take. While space requirement is minimal, the scavenge performance of a tangential sump is poor. A prototype advanced sump was proposed and built with features to address various issues found in the tangential sump.
In this paper, further experimental work on the refinements of the advanced sump is presented. This includes experimental study on the effect of a fence and splitter plate, off-take hole diameter and its location, the effect of gravity by tilting, upstream wall fairing, as well as the depth of the sump itself. The experiments showed that the faired upstream wall modification can reduce residence volume significantly across different operating conditions, indicating improvement in scavenge performance. The other modifications help to reduce residence volume only in certain operating conditions. The results of this study helped towards the birth of an optimized sump design, known as Indy sump. The Indy sump has been accepted as a superior sump design and has been used as a benchmark in many sump design studies.
CFD Driven Analysis of a Multi-Port Pressure Probe for Real Engine Testing
Authors: Lahalle Aude , Fontaneto Fabrizio , Arts Tony 
Published: August 2017

During the development phase of an aircraft engine, extensive ground and flight instrumentation testing is performed. The performance of the instrumentation is quantified in terms of Recovery Factor (RF). Experimental data only provide measurement at the sensor location, but no information is available for the flow field taking place in and around the probe.
The scope of the present paper is to numerically investigate the flow field taking place inside and around a three Kiel heads rake. The study will focus on the description of the flow field and aims at highlighting the mechanisms affecting the RF. Each head has an elliptical casing and contains a pressure sensor (pneumatic pressure tap) and a temperature sensor (thermocouple).
Steady-state RANS simulations have been realized for two different Mach numbers (M = 0.30 and M = 0.65), providing a complete mesh and turbulence models sensitivity analysis. The simulated global flow field demonstrated that regardless of the Mach number, the flow topology is very similar in all cases. The Kiel heads investigation highlighted a well guided flow field confirming the sensors’ high performance.
Gas Turbine Cycle Upgrade and Validation for Heavy Duty Industrial Machines
Authors: Torkaman Alex , Vogel Gregory , Fiebiger Steve , Dietrich Doug , Washburn Ron 
Published: August 2017

Two Siemens Westinghouse SW501F D2 industrial gas turbines were successfully upgraded during a Modified HGP service interval. This paper details the technical aspects of this upgrade and validation of critical turbine blade flutter related parameters during commissioning. Significant performance improvement was achieved by implementation of aerodynamic redesigns of certain compressor and turbine components. An upgraded combustion system and newly installed continuous tuning and health monitoring systems provided operational flexibility and reduction in emissions. Due to historical issues with the 4th stage blade flutter, significant analytical efforts were invested in the structural redesign of the 4th stage blade to predict and avoid flutter and resonance regions. Latest methods of aerodynamic work calculations were employed during design to ensure flutter free operation of this component. Validation steps were implemented using blade tip timing technology to determine synchronous and non-synchronous vibration characteristics of the 4th stage blades during commissioning.
Performance tests per ASME PTC-22 were conducted immediately before and after the outage to provide an accurate measurement of engine performance. Analysis of the performance data after installation and commissioning of the upgrade package confirmed the performance improvement objectives on power output and heat rate were achieved on these two units. Live monitoring and analysis of blade instrumentation data during commissioning and further analysis afterward confirmed flutter free operation of the 4th stage turbine blade.
Computing Fluid Structure Interaction Coupling Time Spectral Method (TSM) and Harmonic Balance Method (HBM)
Authors: Cadel Aude , Ngo Boum Ghislaine , Thouverez Fabrice , Dugeai Alain , Parent Marie-Océane 
Published: August 2017

This paper deals with fluid-structure interactions (FSI), involving a blade profile, submitted to different sources of excitations, as if it were included in a real engine. Two forces of excitation will be considered on the NACA 64A010 airfoil, described in : an external force, due to a forced rotation motion of the blade, and an aerodynamic force, induced by fluid flow around the structure.
By using the Harmonic Balance Method, the airfoil’s motion equation becomes an algebraic problem. Then, this system is solved for each frequency of a chosen range. Therefore, the fluid effect on the translation motion of the profile is studied.
To compute the time periodic aerodynamic field, the Time Spectral Method, implemented in the Onera’s elsA solver, is used for a fast and efficient resolution. This method relies on a time-integration scheme that turns the resolution of the turbulent Navier-Stokes problem into the resolution of several coupled steady state problems computed at different instants of the time period of the movement. The Theodorsen approach with several hypothesis exposed in allows an analytic estimation of the unsteady lift effort. The two approaches are compared for an imposed motion.
In order to predict the dynamic behavior of the system, a fully coupled numerical methodology is developed. For each frequency and at each iteration, TSM supplies the flow field which is used by HBM as a nonlinear excitation on the structure to computate a periodic response and conversely, HBM supplies the new deformed mesh used by TSM to compute the flow field. This strategy has the advantage that all computations take place in the spectral domain, allowing thus to find the steady-state behavior of the fluid and the structure without computing any transient state. The analysis provides the Frequency Forced Response. Some frequencies in the range corresponding to a contribution change between structure and fluid damping are precisely highlighted.
Economic-Competitiveness of Dish-mGT Solar Power Generators
Authors: Gavagnin Giacomo , Sánchez David , Rodríguez José M. , Muñoz Antonio , Martínez Gonzalo S. 
Published: August 2017

This paper provides an analysis of the Optimised Microturbine Solar Power generator (OMSoP) project, funded by the European Commission, as the most recent attempt to develop a dish and mGT Concentrated Solar Power generation system that is cost competitive against photovoltaics, at least in certain business cases. A first section presents the system and business cases along with other boundary conditions (technology levels) and locations of interest. Then, for each case, the specific installed costs assuming a production rate of 1000 units/year are presented as provided by the project partners. Cost reductions as high as 1000 €/kWe are possible through advanced technical specifications (for instance higher turbine inlet temperatures) and complex layouts (cycles including intercooling and reheat), thanks to a major impact on system efficiency and, hence, dish size.
From a techno-economic perspective, the OMSoP technology confirms the potential to become cost-competitive against photovoltaic systems in terms of the cost of electricity. This is discussed in the final section dedicated to project appraisal. The analysis, based on hourly simulations in order to account for offdesign performance, reveals that dish-mGT systems can make a case for certain applications despite having higher installation costs than PV panels. It is shown that under representative boundary conditions, i.e. not in any market worldwide, dish-mGT systems produce electricity at the same levelised cost as small photovoltaic installations (∼11 c€/kWhe).
On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition
Authors: Jiang Hongmei , He Li , Zhang Qiang , Wang Lipo 
Published: August 2017

Modern High Pressure Turbine (HPT) blades operate at high speed conditions. The Over-Tip-Leakage (OTL) flow, which plays a major role in the overall loss generation for HPT, can be high-subsonic or even transonic. In practice from the consideration of problem simplification and cost reduction, the OTL flow has been studied extensively in low speed experiments. It has been assumed a redesigned low speed blade profile with a matched blade loading should be sufficient to scale the high speed OTL flow down to the low speed condition.
In this paper, the validity of this conventional scaling approach is computationally examined. The CFD methodology was firstly validated by experimental data conducted in both high and low speed conditions. Detailed analyses on the OTL flows at high and low speed conditions indicate that, only matching the loading distribution with a redesigned blade cannot ensure the match of the aerodynamic performance at the low speed condition with that at the high-speed condition. Specifically, the discrepancy in the peak tip leakage mass flux can be as high as 22.2%, and the total pressure loss at the low speed condition is 10.7% higher than the high speed case.
An improved scaling method is proposed hereof. As an additional dimension variable, the tip clearance can also be “scaled” down from the high speed to low speed case to match the cross-tip pressure gradient between pressure and suction surfaces. The similarity in terms of the overall aerodynamic loss and local leakage flow distribution can be improved by adjusting the tip clearance, either uniformly or locally. The limitations of this proposed method are also addressed in this paper.
Improvement of Impaired Combustion Conditions at Some Off-Design Operation by Driving a Precisely Controlled Modulation of the Burner Air Feed
Authors: Giuliani Fabrice , Pfefferkorn Lukas , Kraft Gerhard 
Published: August 2017

A non-conventional method based on forced-flow combustion oscillations is investigated regarding the improvement of combustion conditions at suboptimal operating conditions.
In the field of gas turbines, uncontrolled combustion oscillations are called combustion instabilities and they have been extensively studied over the last two decades. Low NOx systems that operate in the lean combustion domain are prone to enable combustion instabilities. A common way to investigate combustion instabilities is to reproduce these with help of an acoustic driver, e.g. using a loudspeaker or a fast valve in order to drive forced-flow combustion oscillations. When the oscillations match with one of the natural resonant frequencies of the combustor cavities or of the feeding pipes, the thermoacoustic coupling can occur in a well-controlled way.
Some positive effects of this type of forcing can be found in the literature. In a similar context, it was shown in a previous work (GT2015-42377) under which conditions and by how far a forced-flow thermoacoustic drive can further push the lean-blow-out limits in the lean region. Following to this work, it is described that driving a resonant flame can also be beneficial regarding combustion quality. Better combustion performances were observed with the help of pulsating the burner air feed at part-load conditions on a premixed swirling flame, where combustion quality is known to be impaired at steady-state.
The presented technology can then be seen as a flexible On-Off thermoacoustic drive, based on forced pulse combustion and using a siren tunable in frequency and amplitude in a refined way. The benefits and the challenges about its hypothetic implementation in the field of turbomachinery conclude this paper.
Characterization of Non-Equilibrium Condensation of Supercritical Carbon Dioxide in a de Laval Nozzle
Authors: Lettieri Claudio , Paxson Derek , Spakovszky Zoltan , Bryanston-Cross Peter 
Published: August 2017

On a ten-year timescale, Carbon Capture and Storage could significantly reduce carbon dioxide (CO2) emissions. One of the major limitations of this technology is the energy penalty for the compression of CO2 to supercritical conditions, which can require up to 15% of the plant’s gross power output. To reduce the power requirements supercritical carbon dioxide compressors must operate at reduced temperatures and near saturation where phase change effects are important. Non-equilibrium condensation can occur in the high-speed flow at the leading edge of the compressor, causing performance and stability issues. The characterization of the fluid at these conditions is vital to enable advanced compressor designs at enhanced efficiency levels but the analysis is challenging due to the lack of data on the metastable fluid properties.
In this paper we assess the metastable behavior and nucleation characteristics of high-pressure subcooled carbon dioxide during the expansion in a Laval nozzle. The assessment is conducted with numerical calculations, supported and corroborated by experimental measurements. The Wilson line is determined via optical measurements in the range of 41 and 82 bar and near the critical point. The state of the metastable fluid is fully characterized through pressure and density measurements, with the latter obtained in a first of its kind laser interferometry set up. In a systematic analysis the inlet conditions of the nozzle are moved close to the critical point to allow for large gradients in fluid properties and reduced margin to condensation. The results of calculations using a direct extrapolation of the Span and Wagner equation of state model are compared with the experimental measurements. The analysis suggests that the direct extrapolation using the Span and Wagner model yields results within 2% of the experimental data, with improved accuracy at conditions away from the critical point. The results are applied in a pre-production supercritical carbon dioxide compressor and are used to define inlet conditions at reduced temperature but free of condensation. Full-scale compressor experiments demonstrate that the new inlet conditions can reduce the shaft power input by 16%.
Development and Evaluation of a Mobile Plant to Prepare Natural Gas for Use in Foam Fracturing Treatments
Authors: Beck Griffin , Poerner Melissa , Hoopes Kevin , Verma Sandeep , Sridhar Garud , Phatak Alhad 
Published: August 2017

Hydraulic fracturing treatments are used to produce oil and gas reserves that would otherwise not be accessible using traditional production techniques. Fracturing treatments require a significant amount of water, which has an associated environmental impact. In recent work funded by the Department of Energy (DOE), an alternative fracturing process has been investigated that uses natural gas as the primary fracturing fluid. In the investigated method, a high-pressure foam of natural gas and water is used for fracturing, a method than could reduce water usage by as much as 80% (by volume). A significant portion of the work focused on identifying and optimizing a mobile processing facility that can be used to pressurize natural gas sourced from adjacent wells or nearby gas processing plants.
This paper discusses some of the evaluated processes capable of producing a high-pressure (10,000 psia) flow of natural gas from a low-pressure source (500 psia). The processes include five refrigeration cycles producing liquefied natural gas as well as a cycle that directly compresses the gas. The identified processes are compared based on their specific energy as calculated from a thermodynamic analysis. Additionally, the processes are compared based on the estimated equipment footprint and the process safety. Details of the thermodynamic analyses used to compare the cycles are provided. This paper also discusses the current state of the art of foam fracturing methods and reviews the advantages of these techniques.
Three-Dimensional Aerodynamic Analysis of a Darrieus Wind Turbine Blade Using Computational Fluid Dynamics and Lifting Line Theory
Authors: Balduzzi Francesco , Bianchini Alessandro , Ferrara Giovanni , Marten David , Pechlivanoglou George , Nayeri Christian Navid , Paschereit Christian Oliver , Drofelnik Jernej , Campobasso Michele Sergio , Ferrari Lorenzo 
Published: August 2017

Due to the rapid progress in high-performance computing and the availability of increasingly large computational resources, Navier-Stokes computational fluid dynamics (CFD) now offers a cost-effective, versatile and accurate means to improve the understanding of the unsteady aerodynamics of Darrieus wind turbines and deliver more efficient designs.
In particular, the possibility of determining a fully resolved flow field past the blades by means of CFD offers the opportunity to both further understand the physics underlying the turbine fluid dynamics and to use this knowledge to validate lower-order models, which can have a wider diffusion in the wind energy sector, particularly for industrial use, in the light of their lower computational burden.
In this context, highly spatially and temporally refined time-dependent three-dimensional Navier-Stokes simulations were carried out using more than 16,000 processor cores per simulation on an IBM BG/Q cluster in order to investigate thoroughly the three-dimensional unsteady aerodynamics of a single blade in Darrieus-like motion. Particular attention was payed to tip losses, dynamic stall, and blade/wake interaction. CFD results are compared with those obtained with an open-source code based on the Lifting Line Free Vortex Wake Model (LLFVW). At present, this approach is the most refined method among the “lower-fidelity” models and, as the wake is explicitly resolved in contrast to BEM-based methods, LLFVW analyses provide three-dimensional flow solutions. Extended comparisons between the two approaches are presented and a critical analysis is carried out to identify the benefits and drawbacks of the two approaches.
An Integrated Conjugate Computational Approach for Evaluating the Aerothermal and Thermomechanical Performance of Double-Wall Effusion Cooled Systems
Authors: Murray Alexander V. , Ireland Peter T. , Rawlinson Anton J. 
Published: August 2017

The drive to further increase gas turbine thermal efficiency and specific power output continue to elevate core temperatures well beyond the natural capabilities of the metals employed in their manufacture necessitating increasingly complex cooling systems.
One such cooling mechanism is the double-wall, effusion-cooled system which combines in a very compact format, many cooling aspects already implemented in gas turbine cooling. To-date, thermomechanical stresses have provided one of the more significant challenges in the implementation of these systems and needs to be considered — alongside aerothermal performance — at the initial stages of design.
This paper presents a novel computational method that has been developed to allow an integrated assessment of both the aerothermal and thermomechanical performance of double-wall cooling geometries. A decoupled conjugate method was developed in which internal cooling performance was ascertained via a conjugate CFD model in which the mainstream flow was not simulated. Instead, external film cooling performance was assessed via a superposition method that was developed and applied to a two-dimensionally varying correlation allowing streamwise film development to be modelled. Results of both the internal and external cooling simulations were then utilised in a conduction model to develop a complete thermal assessment of the geometry. The calculated temperature distribution was used in a thermomechanical FEA analysis permitting an insight into the stress field developed within the double-wall geometry under thermal load.
The developed method was demonstrated in the assessment of seven circular pedestal, double-wall geometries in which a range of geometric parameters were investigated. The results provide an insight into the effect of varying these parameters on both the aerothermal performance of the selected geometries, along with the effect on the thermomechanical stress field developed.
Detailed Analysis of the Wake Structure of a Straight-Blade H-Darrieus Wind Turbine by Means of Wind Tunnel Experiments and CFD Simulations
Authors: Bianchini Alessandro , Balduzzi Francesco , Ferrara Giovanni , Ferrari Lorenzo , Persico Giacomo , Dossena Vincenzo , Battisti Lorenzo 
Published: August 2017

Darrieus Vertical Axis Wind Turbines (VAWTs) have been recently identified as the most promising solution for new types of applications, such as small-scale installations in complex terrains or offshore large floating platforms. To improve their efficiencies further and make them competitive with those of conventional horizontal axis wind turbines, a more in depth understanding of the physical phenomena that govern the aerodynamics past a rotating Darrieus turbine is needed. Within this context, Computational Fluid Dynamics (CFD) can play a fundamental role, since it represents the only model able to provide a detailed and comprehensive representation of the flow. Due to the complexity of similar simulations, however, the possibility of having reliable and detailed experimental data to be used as validation test cases is pivotal to tune the numerical tools.
In this study, a two-dimensional U-RANS computational model was applied to analyze the wake characteristics on the mid plane of a small-size H-shaped Darrieus VAWT. The turbine was tested in a large-scale, open-jet wind tunnel, including both performance and wake measurements. Thanks to the availability of such a unique set of experimental data, systematic comparisons between simulations and experiments were carried out analyzing the structure of the wake, and correlating the main macro-structures of the flow to the local aerodynamic features of the airfoils in cycloidal motion. In general, good agreement on the turbine performance estimation was constantly appreciated.