bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Channel Size on Air-Cooling Performance in Interior Permanent Magnet (IPM) Motor Driving Aviation Fans at High Altitude
Authors: Ito Yu , Watanabe Toshinori , Seki Naoki , Hirakawa Karin , Inoue Tomoya , Himeno Takehiro 
Published: October 2022

Abstract
To enhance worldwide environmental conditions, the air transport industry must drastically reduce carbon dioxide emissions. Electrification of aircraft propulsion systems is one way to meet this demand. In particular, the focus is on obtaining single-aisle aircraft with partial turboelectric propulsion and approximately 150 passenger seats by the 2030s. To develop a single-aisle aircraft with partial turboelectric propulsion, an air-cooled interior permanent magnet (IPM) motor with an output of 2 MW is desired. One of the most difficult problems in air cooling is that air-cooling performance decreases with increasing altitude because the air density decreases. To investigate the effect of altitude on air-cooling performance in the IPM motor, the authors formulated mathematical system equations to describe heat transfer inside the target air-cooled IPM motor, and mathematical analytical solutions were obtained. The most severe condition is the top-of-climb condition. For this condition, a designer should choose cooling air mass flow rates that keep the temperature of the permanent magnets below the maximum temperature limit of 100 °C and the temperature of the coils below the maximum temperature limit of 250 °C. Here, the sizes of the air-cooling channels strongly affect air cooling with the IPM motor. In this paper, the authors briefly review the mathematical formulations and their solutions, investigate the effect of channel size on air-cooling performance in an IPM motor, and explore the optimum configuration and settings for the air cooling channels.
The Nonlinear Thermoacoustic Eigenvalue Problem and Its Rational Approximations: Assessment of Solution Strategies
Authors: Merk Moritz , Buschmann Philip E. , Moeck Jonas P. , Polifke Wolfgang 
Published: October 2022

Abstract
Nonlinear eigenvalue problems (NLEVPs) arise in thermoacoustics by considering the temporal evolution of small perturbations in the relevant governing equations. In this work, two solution strategies are compared: (i) a contour-integration-based method that guarantees to provide all eigenvalues in a given domain and (ii) a method that approximates the NLEVP by a rational eigenvalue problem, which is generally easier to solve. The focus lies on numerical speed, the completeness of the computed spectrum, and the appearance of spurious modes, i.e., modes that are not part of the original spectrum but appear as a result of the approximation. To this end, two prototypical thermoacoustic systems are considered: a single-flame Rijke tube and an annular model combustor. The comparison of both methods is preceded by a detailed analysis of the user-defined input parameters in the contour-integration-based method. Our results show that both methods can resolve all types of considered eigenvalues with sufficient accuracy for applications. However, the recast linear problem is overall faster to solve and allows a priori precision estimates — unlike the contour-integration-based method. Spurious modes as a by-product of the NLEVP approximation are found to play a minor role, and recommendations are given on how to eliminate them.
Comparison of Experimental and Numerical Local Rotational Heat Transfer Effects in a Two-Pass Cooling Channel Configuration
Authors: Gutiérrez de Arcos David , Waidmann Christian , Poser Rico , von Wolfersdorf Jens , Jäppelt Bernhard 
Published: October 2022

Abstract
A two-pass internal cooling channel under the influence of rotation is experimentally and numerically investigated. Steady-state numerical simulations support the experimental method, which is based upon the temperature measurement with thermochromic liquid crystals (TLC). Moreover, the transient TLC experiment serves as a basis for validation of the numerical setup. Reynolds number is 15000, Rotation number is increased up to 0.50 and the cooling channel is investigated at three different angles of attack. Results are locally evaluated as normalized Nusselt number ratios of the rotating to its corresponding non-rotating case. With this, the sole effect of rotation on heat transfer can be disclosed. Histograms of normalized Nusselt number ratio allow for drawing conclusions on the local effects of rotation on heat transfer enhancement.
Compression Applications for Carbon Reduction
Authors: Kurz Rainer , Lubomirsky Matt , McLorg Gregory 
Published: October 2022

Abstract
A In the context of carbon reduction efforts, discussions evolve around hydrogen compression, as well as compression requirements related to CO2 capture, transportation and sequestration. In this paper, compression requirements for these applications are discussed.
The use and creation of hydrogen imposes specific questions on the use of centrifugal compressors. These questions involve the requirement to compress hydrogen for significant pressure ratios, and the impact of transporting hydrogen in pipelines, or by other means. Part of the discussion is also the location of blue hydrogen production versus green hydrogen production, based on the fact that transport of CO2 or natural gas requires less energy than the transport of hydrogen.
Further, carbon sequestration by capturing, transporting and sequestering CO2 from the exhaust of fossil fired power plants, from the generation of blue hydrogen, or the generation of Ammonia is discussed. Compression duties include the compression from capture pressure to pipeline pressure, the boost compression as part of the pipeline transport, and the compression required to sequester the CO2. Issues addressed in this part include the relative effort required based on the CO2 concentration in the exhaust, and methods to compress CO2 and CO2 mixtures from close to atmospheric pressure to pipeline pressure.
In this discussion, the option of transporting hydrogen to a power plant versus transporting natural gas to said power plant, and transporting captured CO2 back to a sequestration site, is evaluated, and the conclusion is supported with data.
The Effect of Partial-Load Operation on a Gas Turbine Compressor of an Advanced Combined Cycle Power Plant
Authors: Hagita Yasuharu , Miyazawa Hironori , Furusawa Takashi , Yamamoto Satoru , Yonezawa Koichi , Umezawa Shuichi , Ohmori Shuichi , Suzuki Takeshi 
Published: October 2022

Abstract
Gas turbine combined cycle (GTCC) power plants daily undergo start-up, shutdown and partial-load operations to maintain load invariance of electric power supply. The off-design conditions in this process may give rise to unexpected and unsteady flow behavior in the gas turbine, resulting in fatigue failure. JERA Co. Inc. currently operates gas turbines at many advanced combined cycle (ACC) power plants using a start-up and a partial-load operations. During the start-up procedure, some machine vibrations were reported at the ACC power plant when acoustic emission (AE) measurements were applied to the gas turbine compressor. A small crack in the first-stage stator blade was found at another unit during the overhaul. The partial-load operation may be in a similar condition to that in the startup procedure.
This study elucidated the cause of machine vibration measured in an actual gas turbine compressor of an ACC power plant using full-annulus flow computation to indicate the possibility of blade failure. The full-annulus unsteady flows through the inlet guide vanes (IGV) and 1.5 rotor and stator stages in the compressor were simulated. The frequency of the simulated vibration was compared with that of the natural vibration of the blades, which was obtained by conducting eigenvalue analysis. The results for the partial-load condition captured an abnormal vibration resulting from a rotating stall. The rotating stall frequency closely matched the second-mode frequency of the first-stage stator blade’s natural vibration. This result suggests that the partial-load condition could be related to the cause of the blade failure due to the blade vibration.
The Effect of Casing Coolant Injection on Aerodynamic Loss in a Linear Turbine Cascade With Tip Clearance
Authors: Hong Dunam , Choi Minsuk , Kim Myungho , Song Seung Jin 
Published: October 2022

Abstract
Deviation and loss have been measured and numerically analyzed in a linear turbine cascade with tip clearance and upstream casing coolant injection. Compared to the case without coolant injection, when a coolant flow of 0.5% of the mainstream mass flow rate with a non-dimensional swirl of 100% is injected into the mainstream, the following changes occur. The mass-averaged deviation decreases by 2.4 degrees. The decrease in deviation occurs mainly because the underturning and overturning due to the passage vortex (PV) and trailing shed vortex (TSV) increase; and the centers of both vortices move toward the midspan and pressure side. The mass-averaged loss increases by 15.9% primarily because the losses associated with the PV and TSV increase. Multiple vortices are formed at the exit of the coolant slot due to the Kelvin-Helmholtz instabilities. These slot exit vortices strengthen the PV and increase the associated loss, but they have little direct interaction with either tip clearance vortex (TCV) or TSV. The TSV is strengthened by both tip unloading and PV strengthening, and thus the associated loss increases. The loss due to the TCV decreases slightly due to the reduced incidence and decreased tip clearance flow rate. When the coolant is injected with less swirl — with non-dimensional swirl values of 85% and 70% — the loss increases are reduced to 9.3% and 6.7%, respectively, relative to the case without coolant. The change in loss with decreasing swirl is mainly due to the decreases in PV and TSV losses. The loss in the tip region is not sensitive to the coolant swirl.
Influence of Porosity on Double-Walled Effusion-Cooled Systems for Gas Turbine Blades
Authors: Courtis Matthew , Ireland Peter 
Published: October 2022

Abstract
Double wall effusion cooling (DWEC) systems for gas turbine blades utilise two skins connected by pedestals and take advantage of cooling benefits provided by impingement jets and film holes. The latter exhausts coolant externally onto the blade surface forming a protective layer against the high external heat loads, which can be enhanced via the beneficial influence of adjacent films. Consequently, increasingly porous outerskins are being considered in order to provide greater thermal protection and/or reduce the required coolant mass consumption. To realise such systems, further research must understand how the internal aerothermal field is affected by high porosity.
A semi-decoupled unit-cell computational fluid dynamics (CFD) method is applied to a range of DWEC systems to understand overall cooling effectiveness as well as internal characteristics. A comparison of internal convection highlights a shift in the breakdown of cooling performance, due to the large changes in wetted surface area of the outerskin. For low porosity, most of the internal cooling occurs through the jet impingement on the internal outerskin wall, while the addition of more film holes provides an increasingly greater proportion of convective heat transfer. On the external surface, porosity increased film effectiveness due to film superposition, provided a more uniform film coverage, and reduced the likelihood of jet-lift-off.
Coupling the benefits of internal cooling and film effectiveness resulted in a reduction of mean metal temperature, peak temperature and temperature gradient between the outer and inner walls. Criteria reflecting the main drivers for thermal fatigue. Despite these benefits, for the most porous DWEC configuration a variation in mass flow between film holes was observed, and in some cases the risk of hot gas ingestion was evident. DWEC components would benefit from further understanding of the susceptibility to blockage, the pressure margin limits and the extent of flow migration.
Numerical Investigation of Unsteady Flow Phenomena in a Centrifugal Compressor Operating Near Surge With a Geometrically Reduced Model
Authors: Paul Dominik , Eißler Werner 
Published: October 2022

Abstract
Deep surge is a time and system dependent phenomenon that might be triggered by a flow instability. This instability could be subsequently used as an indicator for the surge margin. Based on former numerical investigations concerning steady flow phenomena in a centrifugal compressor, published at “Turbo Expo 2021” by Hochschule RheinMain and TU Darmstadt the investigations have been continued. A speed line is divided into four sections based on its slope, which are examined for instabilities by means of transient simulations with a numerical reduced model. For this purpose, a detailed frequency analysis is carried out to detect unstable flow behaviour. It is shown that the characteristic of the speed line is in a good agreement with the analysed frequency spectrum and the associated unsteady flow phenomena. These are for instance a highly changing incidence triggered by vortex tubes at the impeller inlet. In addition, the computations show an instability in the vaneless space behind the trailing edge, the occurrence of which is in a relationship to the experimental stability limit. Regardless of the system volume, the phenomenon could be used as an indicator for the stability of the compressor wheel.
A second speed line is then used to validate this relationship.
Investigation of a High-Pressure Turbine Stage in a High-Speed Rotating Transient Test Facility for Rotor Tip Study and a Parametric Study for Improved Heat Transfer Calculation
Authors: Singh Deepanshu , Beard Paul F. , Cardwell David , Chana Kam S. 
Published: October 2022

Abstract
The first part of the paper presents commissioning of a single-stage high-pressure turbine employed in a series of extensive experiments to study the aerodynamics and heat transfer on the rotor surface and casing liner. The OTRF (Oxford Turbine Research Facility), a high-speed rotating transient test facility has the capability to take unsteady aerodynamic and heat transfer measurements at engine representative conditions with a variety of inlet temperature profiles including radial distortion and swirl. A temperature profile survey was conducted at the inlet of the high-pressure NGV (Nozzle Guide Vane). Static and total pressure and temperature measurements have been taken at various locations on the rig including NGV surface, inlet and exit, and rotor exit to establish rig operating conditions. Detailed description of mass flow rate measurements along with calculation of heat loss factor in the rig is presented. The second part of the paper presents a parametric study performed to improve heat transfer measurement calculations from high-frequency response thin-film gauges. The effect of parameters like material properties and thickness of substrate on heat flux has been studied. A detailed uncertainty analysis for heat flux is also presented. A thermal model calibrated with analytical solutions has been developed to optimise thin-film gauge configurations and to study side-conduction effects.
Hexavalent Chromium Observations on Serviced Components of Oil&Gas Gas Turbines: Formation Mechanism Study
Authors: Scrinzi Erica , Mochi Gianni , Melani Antonio , Del Puglia Eugenio , Pranzetti Alice 
Published: October 2022

Abstract
Hexavalent chromium Cr(VI) is one of the oxidation states (+6) of chromium. It is a recognized toxin and carcinogen, which if ingested or inhaled may affect the respiratory system, kidneys, and liver. It can also cause dermatitis and severe irritation to the eyes. It is widely present in electroplating, anodizing and dye production industries, but has recently been identified as contaminant on serviced components of gas turbines. To this regard, there is the potential for Cr(VI) compounds to be present on gas turbine components serviced at high temperature, if calcium-containing insulating, anti-seize or sealing products are used.
A systematic experimental campaign was carried out to investigate the mechanism and understand the influence of various factors on the formation of substances containing chromium in the hexavalent form. During the test campaign, anti-seize products, sealing products, insulating products but also environmental contaminants were tested on different bare materials in different service conditions.
Advanced Tip Repair of Single Crystal HPT Blades With LW3 and LW4280 Welding Materials
Authors: Chan Anthony , Gontcharov Alexandre , Lowden Paul , Mikolajewski Thomas , Sixsmith J. J. , Tollett Robert , Greer Clayton 
Published: October 2022

Abstract
High pressure turbine (HPT) blades manufactured from single crystal (SX) materials exhibit tip degradation during service resulting in loss of coatings and parent metal, primarily from abrasion, thermal-mechanical fatigue cracking (TMF), creep, and oxidation. Currently, Gas Tungsten Arc Welding (GTAW) and Laser Beam Welding (LBW) with Merl 72 and Rene 142 (R142) welding materials are used for repairing the tips of SX HPT blades. Tips repaired with Merl 72, despite the superior oxidation resistance of the cobalt welding material, are prone to cracking due to the low mechanical properties of the Merl 72 welds at temperatures exceeding 1800°F (982°C). Additionally, despite the high strength of R142 in its cast condition, R142 welds are prone to weld stress-strain cracking and thus require preheating of the blades above 1700°F (926°C) to repair the part with a predetermined level of micro cracking present. Preheating can adversely affect the inert atmospheric conditions of the argon protection. This inadequate shielding of the welding area may result in contamination of welds with non-metallic inclusions which reduce creep and TMF properties.
The current study focuses on substantiating the replacement of Merl 72 with alternative LW3 and LW4280 nickel based welding materials for minor dimensional restoration and full tip replacement on SX HPT blades with a solid tip cap. LW3 and LW4280 contain 28 vol.% and 49 vol.% gamma prime phase respectively, after post weld aging heat treatment. A time-transient thermal mechanical Finite Element Analysis (FEA) of the SX HPT blade was completed for takeoff, cruise, and landing conditions. The resultant temperature and stresses from the FEA study were used as the basis for qualification of the tip repair. Tensile and stress rupture properties of dissimilar SX-LW3 and SX-LW4280 welds produced at ambient temperature using manual GTAW and Laser Direct Energy Deposition (L-DED) on a LAWS1000 welding system utilizing a 3D additive manufacturing (AM) concept were studied. It was demonstrated that LW4280 welds had superior stress rupture, and fatigue properties when compared to M 72. Cyclic oxidation resistance of LW4280 at 2048°F (1120°C) was found to be sufficient to ensure required durability of repaired blades for 6,000 cycles in cases of damage to protective coatings. Some examples of repairs of HPT blades developed using these materials and technologies are provided.
A Coupled Computational Aero-Acoustics (CAA)/ Large-Eddy Simulation (LES) Approach for the Pressure Calculation in Internal Low-Mach Number Flows
Authors: Bénez Pierre , Lartigue Ghislain , Moureau Vincent , Ribert Guillaume , Robin Marine 
Published: October 2022

Abstract
The predictive unsteady simulation of pressure fluctuations in turbulent internal flows at low-Mach number is challenging because of the very different propagation speeds of the acoustic and entropy waves. In this paper, a hybrid Computational-Aero-Acoustics (CAA) / Large-Eddy-Simulation (LES) approach tailored for the numerical calculation of aero-acoustic noise and pressure in internal low-Mach number flow is developed to alleviate the acoustic time step restriction. The algorithm is based on the coupling of a fractional-step method used to solve the low-Mach number Navier-Stokes equations and a fully-implicit linear acoustics solver. The pressure field resulting from the Helmholtz equation computed by the acoustic solver is composed of both dynamic and acoustic contributions. The Newmark’s time integration method combined with implicit Non-Reflecting-Boundary-Conditions (NRBC) are implemented for solving implicitly the Helmholtz equation and then advancing the two solvers with the same convective time step. The properties of the linear acoustic solver are illustrated on simple test cases and the coupling method is then validated by performing the aero-acoustic simulation of the isothermal flow in a complex semi-industrial burner.
Modeling Power Constraints Using Maps and Field Data in Optimization Problems for Gas Transportation Systems
Authors: Allen Cody W. 
Published: October 2022

Abstract
Gas transmission networks have been and continue to be the most efficient method for transporting natural gas. As Hydrogen begins to emerge as one possible solution of renewable energy and starts mixing into gas networks, now more than ever, efficient operation is paramount. Part of the efficient pipeline operation puzzle is knowing how much power is available at a given compressor station, which constrains the head and flow that can be produced. This paper derives and implements driver constraints relating to gas pipeline optimization problems such as throughput maximization and compressor station power minimization at the pipeline level. In the literature the driver is often neglected in implementations of pipeline optimization problems. Often, only the compressor map is considered during the optimization procedure. In this work we develop the necessary physical relations and constraints between the gas compressor and driver. The addition of these constraints ensures that solutions are not only bounded by surge and stonewall curves as well as compressor speed, but also by available power from the driver given current ambient conditions. We also derive a method to fit constraints to observed data. The modified optimization problem results in more accurate solutions of pipeline optimization problems, giving operators more accurate data with which to make business decisions and operate pipelines.
Micromechanical Modeling of Time-Dependent Crack Opening Behavior in SiC/SiC Composites
Authors: Li Longbiao 
Published: October 2022

Abstract
Ceramic-matrix composites (CMCs) possess high specific strength and modulus at elevated temperature and have already been applied in hot-section components in commercial or military gas turbine engines. Due to low fracture strain in the brittle SiC ceramic, matrix microcracking occurs below the proportional limit stress (PLS). At elevated temperature, the opening of matrix microcracking affects the mechanical properties of CMCs when the oxygen or oxidative gas ingresses the composite through these cracks. To ensure the reliability, safety, and airworthiness level of CMCs components, it is necessary to understand the crack opening behavior of CMCs at elevated temperature. In this paper, a micromechanical approach is developed to predict the time-dependent crack opening behavior in SiC/SiC composite. Micro stress field in the different damage regions are obtained and the cracking opening displacement (COD) are calculated. Experimental CODs in SiC/SiC composite for different matrix crack lengths are predicted. Effects of composite material properties, stress level, and testing temperature on the time-dependent crack opening behavior in SiC/SiC composite are analyzed. Relationships between the cracking opening, composite’s constituent properties, stress level, and testing temperature are established. The analysis results can help the engineering designer better understanding the crack opening behavior in CMCs.