bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laboratory and On-Site Findings Demonstrating the Greater Effectiveness of Biphase Water-Based Compressor Cleaners Over Monophase Cleaners
Authors: Kloter Simon , Ashford Neil F. , Fitchett Duncan R. 
Published: November 2019

Abstract
Compressor washing is a widely applied method to reduce the fouling rate of compressor blades by on-line washing and restore lost power by off-line washing. One of the factors influencing the effectiveness of a wash procedure is the efficiency of the detergent used for washing. This especially in the presence of hydrophobic contamination such as oily and carbon type deposits that can be difficult to penetrate and loosen by water-based detergents.
In this paper, a comparison of cleaning performance is made between monophase water-based compressor cleaners and a biphase water-based compressor cleaner.
Most of the currently used water-based compressor cleaners are monophase solutions. Their main active ingredients are surfactants which lower surface tension and interfacial tension allowing detachment and emulsification of foulant from a compressor blade. Biphase compressor cleaners are also formulated with surfactants, however due to their sub-micron heterogeneous nature they not only provide detachment and emulsification but a much more effective capability to solubilize even hydrocarbon type contamination.
Cleaning efficiencies of these cleaners were evaluated in the laboratory using various test methods including US MIL-PRF-85704C. All of these performed tests confirm the significantly higher effectiveness of the biphase compressor cleaner.
To validate the results from the laboratory tests a direct comparison of a monophase cleaner and a biphase cleaner was performed at a power station in the UK. After about four years of frequent washing with the monophase cleaner on two engines, one GT was then washed three times consecutively offline within a time period of six months with the biphase cleaner. In the second GT, washing was continued with the monophase cleaner. The visual inspection during a major overhaul very clearly showed a significantly higher removal of contamination from the GT washed with the biphase compressor cleaner.
An Advanced Single-Stage Turbine Facility for Investigating Non-Axisymmetric Contoured Endwalls in the Presence of Purge Flow
Authors: Jones Robin R. , Pountney Oliver J. , Cleton Bjorn L. , Wood Liam E. , Schreiner B. Deneys J. , Figueiredo A. J. Carvalho , Scobie James A. , Cleaver David J. , Lock Gary D. , Sangan Carl M. 
Published: November 2019

Abstract
In modern gas turbines, endwall contouring (EWC) is employed to modify the static pressure field downstream of the vanes and minimise the growth of secondary flow structures developed in the blade passage. Purge flow (or egress) from the upstream rim-seal interferes with the mainstream flow, adding to the loss generated in the rotor. Despite this, EWC is typically designed without consideration of mainstream-egress interactions. The performance gains offered by EWC can be reduced, or in the limit eliminated, when purge air is considered. In addition, EWC can result in a reduction in sealing effectiveness across the rim seal. Consequently, industry is pursuing a combined design approach that encompasses the rim-seal, seal-clearance profile and EWC on the rotor endwall.
This paper presents the design of, and preliminary results from a new single-stage axial turbine facility developed to investigate the fundamental fluid dynamics of egress-mainstream flow interactions. To the authors’ knowledge this is the only test facility in the world capable of investigating the interaction effects between cavity flows, rim seals and EWC. The design of optical measurement capabilities for future studies, employing volumetric velocimetry and planar laser induced fluorescence are also presented. The fluid-dynamically scaled rig operates at benign pressures and temperatures suited to these techniques and is modular. The facility enables expedient interchange of EWC (integrated into the rotor bling), blade-fillet and rim-seals geometries.
The measurements presented in this paper include: gas concentration effectiveness and swirl measurements on the stator wall and in the wheel-space core; pressure distributions around the nozzle guide vanes at three different spanwise locations; pitchwise static pressure distributions downstream of the nozzle guide vane at four axial locations on the stator platform.
A Novel Methodology for Detecting Foreign Object Damage on Compressor Blading
Authors: Voigt Paul , Voigt Matthias , Mailach Ronald , Münzinger Daniel , Abu-Taa Kimon , Lange Alexander 
Published: November 2019

Abstract
Foreign Object Damage (FOD) to compressor airfoils is a common problem in operating aircraft engines that occurs when objects or debris are sucked into the engines. Especially small surface defects or impact damage (100μm – 300μm depth) can be problematic, as it only becomes noticeable during engine maintenance process, but can have a strong influence on the fatigue strength and service life of individual airfoils.
Usually the blade and vane inspection during maintenance is carried out by visual examinations. The inspection findings are individually assessed and as a result the airfoils are accepted, repaired or replaced. This manual inspection process has a significant optimization potential by the means of automatization. This paper presents a novel methodology to automatically detect FOD on compressor airfoils. For the investigation and validation, numerous used compressor blades and vanes were digitized on site with a high precision optical 3D scanning system.
A first approach is based on a machine learning algorithm. The idea is the surface segmentation of the digitized airfoil into typical affected areas such as the leading edge (LE), trailing edge (TE), pressure side (PS) or suction side (SS), wherein irregularities during the segmentation can be an indication for FOD. For a second approach, the surface curvature of the airfoil is considered. Locally limited regions with high curvature and concave shapes are sought as an indication for FOD. The required parameters position and depth associated to the individual FOD are calculated in both approaches. The results of both approaches are compared to each other and are validated against the results of a commercial software tool, which uses the approach of digital stoning to create surface defect maps. Furthermore, the results are verified by manually examining the airfoil scans.
In the case of relatively small FOD, both approaches generate meaningful results. In terms of larger damages and deformations, both approaches have difficulties detecting it. This problem can be compensated by parametrization of the scanned airfoils with a section based approach using NACA like profile parameters. Unusual changes of specific airfoil parameters (e.g. stagger angle and chord length) over the airfoils height can indicate large FOD or deformation.
Tailored Fuel Treatment Enables Optimizing the Operation of Heavy-Fueled Gas Turbines
Authors: Vierling Matthieu , Moliere Michel , Aboujaib Maher , Sokolov Dmitry , Catrin Sven , Glaser Paul , Denolle Richard , Marikkar Nuhuman , Tharindu Jayath , Egodawatta Kithsiri , Montagne Pierre 
Published: November 2019

Abstract
The combustion of heavy fuel oil (HFO) in gas turbines (GT) generates some operational constraints and expenses which are too often accepted fatalistically.
A first development has addressed the technical challenge caused by the deposition of ash on the hot parts of the turbines. Indeed, the combustion of HFO significantly increases the volume of ash as one must treat the fuel with a “vanadium inhibitor” that acts as an ash modifier preventing hot corrosion by vanadium. This fouling effect is the most serious drawback of HFO operation as it progressively shrinks the performances and reduces the availability of the machines. To tackle this issue, a genuine bimetallic vanadium inhibitor has been developed and field tested step by step between 2015 and 2018.
The last step that took place at Yugadanavi in March-April 2018 has allowed validating a ready-to-use version of this bimetallic inhibitor product. Upon the completion of this program, the rate of power degradation during HFO operation has been halved and the GT availability significantly increased while the emission of particulates has been substantially reduced.
As a further improvement effort, the teams have tested in the field the effect of changing the temperature of the HFO on its viscosity and monitored the impact induced on the quality of fuel atomization that underlies namely the level of particulate emissions. This second program devoted to the optimization of HFO heating, has enabled defining a rational minimum temperature of the fuel which establishes a fair compromise between atomization effectiveness and thermal energy consumption.
This paper summarizes the main outcome of this multi-year collaborative test program.
LES-Conjugate Heat Transfer Analysis of a Ribbed Cooling Passage Using the Immersed Boundary Method
Authors: Oh Tae Kyung , Tafti Danesh , Nagendra Krishnamurthy 
Published: November 2019

Abstract
The present study focuses on evaluating fully-coupled conjugate heat transfer simulation in a ribbed cooling passage with a fully developed flow assumption using LES with the immersed boundary method (IBM-LES-CHT). The IBM-LES and the IBM-CHT frameworks are validated prior to the main simulations by simulating purely convective heat transfer in the ribbed duct, and a laminar boundary layer flow over a 2D flat plate with heat conduction, respectively. For the main conjugate simulations, a ribbed duct geometry with a blockage ratio of 0.3 is simulated at a bulk Reynolds number of 10,000 with a conjugate boundary condition applied to the rib surface. The nominal Biot number is kept at 1, which is similar to the comparative experiment. As a means to overcome a large time scale disparity between the fluid and the solid regions, the use of a high artificial solid thermal diffusivity is compared to the physical diffusivity. It is shown that while the diffusivity impacts the instantaneous fluctuations in temperature, heat transfer and Nusselt numbers, it has an insignificantly small effect on the mean Nusselt number. Comparison between IBM-LES-CHT and iso-flux heat transfer simulations shows that the iso-flux case predicts higher local Nusselt numbers at the back face of the rib. Furthermore, the local Nusselt number augmentation ratio (EF) predicted by IBM-LES-CHT is compared to experiment and another LES conjugate simulation. Even though there is a mismatch between IBM-LES-CHT predictions and other two studies at the front face of the rib, the area-averaged EF compares reasonably well in other regions between IBM-LES-CHT prediction and the comparative studies.
The Effect of the Corner Recirculation Zone on Separated Stratified Swirling Flames and Combustion Instabilities
Authors: Song Heng , Han Xiao , Lin Yuzhen , Zhang Chi , Hui Xin , Wang Xinyao , Sung Chih-Jen 
Published: November 2019

Abstract
The present work investigates effects of the corner recirculation zone (CRZ) on flame macrostructures and combustion instabilities in the Beihang Axial Swirler Independently Stratified (BASIS) burner, a double-swirled full-scale burner characterized by separated stratified swirling flames at atmospheric pressure supplied with methane/air mixture. Three different macrostructures are observed, i.e. a lifted L-flame, a double-conical S-flame and a single conical V-flame as the stratification ratio (SR, the ratio of the inner stream equivalence ratio to the outer stream equivalence ratio) varies from 0.25 to 2.50 at a fixed total equivalence ratio of 0.6. It is found that the penetration of the flame into the corner recirculation zone leads to a sudden increase of acoustic oscillation. Rayleigh index maps confirm the driving effect of the CRZ region on combustion instabilities for the 0.25 ≤ SR ≤ 1.75 cases. When the corner recirculation zone is removed by the use of segmented confinements, similar flame macrostructures arise in the same SR range. More interestingly, the combustion instability is suppressed under all stratification ratios. A parametric experiment is also performed to confirm the generality of above findings, including three types of the segmented confinement, two premixednesses of the outer flame and a wider range of operating conditions. The suppressive effect is outstanding in all segmented confinements. The present study reveals the effect of the corner recirculation zone on combustion instabilities and demonstrates a potential method for passive control.
High Power Steam Turbine Lifetime Increase by Means of Front End Seal Arrangement and Start-Up Heating Conditions Improvement
Authors: Moroz Leonid , Kochurov Roman , Bakhmutska Julija , Goloshchapov Vladimir 
Published: November 2019

Abstract
Use of high power steam turbines in maneuver regimes by power plants became a widely-distributed practice in chase of short-term economic benefits. At the same time, these actions resulted in much higher levels of lifetime consumption for turbines which are not designed for high numbers of start-ups.
The purpose of the present study is to improve operational flexibility for 325 MW steam turbine through design modifications.
For the accurate simulation of rotor thermo-structural state and lifetime, an improved methodology was developed. The approach allows engineers to account for the steam film condensation process and the steam flow physics for regions with the anticipated high-stress levels at front-end seal zone, and the influence of the inter-casing space steam film condensation on the flow parameters in the front-end seals chambers.
Based on the simulation results for the 325 MW supercritical steam turbine HP rotor, the design changes of the front-end seal arrangement and heating conditions modification during the pre-warming phase are proposed. The results show that the proposed changes make it possible to provide a more uniform heating and lower thermo-stress level for the high-pressure cylinder rotor at the front-end seal region during the pre-warming phase, which results in an increased allowable number of turbine start-ups.
The influence of heating conditions on thermo-stresses and low cycle fatigue lifetime for the baseline and modified designs as well as modeling details for transient thermo-structural analysis have been discussed.
Efficient Design Investigation of a Turbofan in Distorted Inlet Conditions
Authors: Godard Benjamin , De Jaeghere Edouard , Gourdain Nicolas 
Published: November 2019

Abstract
Designing a turbofan to operate in distorted inlet conditions is an issue of growing interest. In such conditions however, fan design can be computationally challenging. Indeed, subject to neither axi-symmetrical nor periodic inlet conditions, computations must be carried out throughout the whole circumferential domain i.e. 360°. Besides, the classical CFD approach implies the use of URANS computations so as to capture the distortion transfer across the fan stage. Eventually, computations are too onerous to be used in design loops. In this context, this paper presents a methodology to effectively assess a fan blade design domain in distorted conditions. This methodology is based on a body-force source term approach formulated in order to accurately recreate deviations, loads and losses across the fan stage. It notably enables to gain two orders in terms of restitution time and thus the possibility to use optimization tools. The design domain of this study is based on variations of profile chord, blade leading and trailing edges angles applied at two different relative heights. A Latin Hypercube Sampling (LHS) associated with a meta-model based on Radial Basis Functions (RBF) enables to assess the impact of geometric variations on performance and operability. Although this study emphasizes that some modeling improvements are still necessary, it also demonstrates the potential of the body-force methodology to conduct fan design when subject to inlet distortion.
Laminar Flame Speed Experiments of Alternative Liquid Fuels
Authors: Keesee Charles L. , Guo Bing , Petersen Eric L. 
Published: November 2019

Abstract
New laminar flame speed experiments have been collected for multiple alternative liquid fuels. Understanding the combustion characteristics of these synthetic fuels is an important step in developing new chemical kinetics mechanisms that can be applied to real fuels. Included in this study are two synthetic Jet fuels: Syntroleum S-8 and Shell GTL. The precise composition of these fuels is known to change from sample to sample. Since these are low vapor pressure fuels, there are additional uncertainties in their introduction into gas-phase mixtures, leading to uncertainty in the mixture equivalence ratio. An in-situ laser absorption technique was implemented to verify the procedure for filling the vessel and to minimize and quantify the uncertainty in the experimental equivalence ratio. The diagnostic utilized a 3.39-μm HeNe laser in conjunction with Beer’s Law. The resulting spherically expanding flame experiments were conducted over a range of equivalence ratios from φ = 0.7 to φ = 1.5 at initial conditions of 1 atm and 403 K in the high-temperature, high-pressure constant-volume vessel at Texas A&M University. The experimental results show that both fuels have similar flame speeds with a peak value just under 60 cm/s. However, it is shown that when comparing the results from different data sets for these real fuels, equivalence ratio is not necessarily the best parameter to use. Fuel mole fraction may be a better parameter to use as it is independent of the average fuel molecule or fuel surrogate used to calculate equivalence ratio in these real fuel/air mixtures.
A New Structural Bump Foil Model With Application From Start-Up to Full Operating Conditions
Authors: Arghir Mihai , Benchekroun Omar 
Published: November 2019

Abstract
The paper presents a new structural bump foil model that can handle all operating conditions from start-up to full speed. The model is based on a non-linear contact algorithm with friction and gaps. The top foil is modeled as a curved beam while bump foil uses a coupled truss model.
The model considers the gaps between the bump foil and the bearing casing, between the bump foil and the top foil and between the rotor and the top foil. Thus, any numerical interference between the rotor and the top foil is avoided. A mixed lubrication model is used for the thin film pressures. Following this algorithm, contact pressures appear if the film thickness is less than three times the equivalent roughness of the rotor and of the top foil. Fluid pressures are calculated from numerical solutions of Reynolds equation while contact pressures, if present, are calculated with the model of Greenwood and Williamson.
The model is validated by comparisons with the experimental results obtained for start-up operating conditions of a first generation foil bearing of 38.1 mm diameter with static loads of 10 N to 50 N. Theoretical predictions of the start-up torque and take-off speed compare well with experimental results. It is also shown how manufacturing bump height errors can explain the differences between theoretical and experimental predictions.
Further validations are presented for the same bearing operating at high speeds (30, 45 and 55 krpm) and heavy static loads (up to 200 N). The calculated minimum film thickness and attitude angle are compared with experimental data from the literature.
Modeling and Control of a Supercritical CO2 Water Cooler in an Indirect-Fired 10MWe Recompression Brayton Cycle Near Critical Conditions
Authors: Liese Eric , Mahapatra Priyadarshi , Jiang Yuan 
Published: November 2019

Abstract
A one-dimensional design and dynamic model of a microtube heat exchanger is presented for cooling supercritical CO2 to near critical conditions (35°C and ∼90 bar) with water. A control strategy is designed and implemented to achieve a desired hot-side CO2 outlet temperature, while the cooling-water exit temperature is monitored (ideally kept below 50°C). The control responses during drastic process changes at the boundaries such as sCO2 inlet flow/pressure and cooling water inlet temperature are presented.
Effect of APS Flash Bond Coatings on Furnace Cycle Lifetime of Disks and Rods
Authors: Pint Bruce A. , Lance Michael J. , Haynes J. Allen , Gildersleeve Edward J. , Sampath Sanjay 
Published: November 2019

Abstract
Air plasma sprayed (APS) flash coatings on high velocity oxygen fuel (HVOF) bond coatings are well known to extend the lifetime of thermal barrier coatings. Recent work compared flash coatings of NiCoCrAlY and NiCoCrAlYHfSi applied to both rods and disk substrates of alloy 247. For rod specimens, 100-h cycles were used at 1100°C in wet air. Both flash coatings significantly improved the lifetime compared to HVOF-only and VPS-only MCrAlY bond coatings with no statistical difference between the two flash coatings. For disk specimens tested in 1-h cycles at 1100°C in wet air, the NiCoCrAlY flash coating significantly outperformed an HVOF-only NiCoCrAlYHfSi bond coating and a NiCoCrAlYHfSi flash coating. The flash coatings formed a mixed oxide-metal zone that appeared to inhibit crack formation and extend lifetime. In addition to the flash coating increasing the bond coating roughness, the underlying HVOF layer acted as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. The lower Y+Hf level in the Y-only flash coating appeared to minimize oxidation in the flash layer, thereby increasing the benefit compared to a NiCoCrAlYHfSi flash coating.
Multi-Disciplinary Design Optimization of a Horizontal Micro Kaplan Hydro Turbine
Authors: Amano Ryoichi S. , Abbas Ahmad I. , Qandil Mohammad D. , Al-Haddad Muhannad R. 
Published: November 2019

Abstract
This study investigates a performance-based design optimization for a Kaplan hydro turbine at a maximum water head of 2.6 m (8.5 ft), micro-sized horizontal Kaplan turbine with 7.6 cm (3.0 in) diameter that is featured fixed blades to attain the optimum performance for such type and size of hydro turbines. Optimization process includes solving design problems and enhance design development by applying a multi-disciplinary design optimization (MDO) technique. Varying the geometrical parameters of the turbine, i.e., dimensions, number of blades, blade wrap angles, and different rotational speeds (500–3000 RPM) are the relevant proposed disciplines of this study.
An in-house code is used for optimizing the geometrical parameters of the turbine. A numerical solution that utilizes computational fluid dynamics (CFD) for a 3D, turbulent, transient unsteady and swirl flow is developed using STAR-CCM+ software in conjunction with an experimental setup of a lab-sized closed-loop water system for validation. The performance of the turbine is predicted by evaluating the power output (in watts), mesh independency analysis is also presented for CFD results validation.
Two multi-simulation matrices were solved by using the high-performance computing (HPC) cluster of the University of Wisconsin-Milwaukee. First matrix includes different number of the blades (3, 4, 5, 6, and 7 blades) over six different rotational speeds (500, 1000, 1500, 2000, 2500, and 3000), while the second matrix includes 121 possible combinations of blade wrap angles starting at 60°-60° (hub-shroud) angle to 110°-110° angle with 5° increment alternated at both sides, the hub and the shroud.