bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Higher Water Vapor Content in H2-Fired Turbines on High Temperature Durability
Authors: Pint Bruce A. , Pillai Rishi , Romedenne Marie , Dryepondt Sebastien 
Published: September 2023

Abstract
Water vapor is a constituent in many environments of technical significance, especially those associated with combustion, and the switch to hydrogen-firing will increase the concentration of water vapor in the exhaust. A negative influence of water vapor on high temperature oxidation has long been recognized for both metallic and ceramic components by comparing laboratory exposures with and without water vapor. However, the effect of water vapor concentration has not been studied as frequently. Several data sets will be reviewed including alloys for thin-walled gas turbine recuperators and the performance of uncoated superalloys and alumina-forming alloys and coatings including the performance of thermal barrier coatings in furnace cycle testing. Chromia-forming alloys are more severely degraded by water vapor in exhaust due to the volatilization of CrO2(OH)2 and this reaction may be faster with higher water vapor contents. Alumina-forming alloys and coatings exhibit some degradation with the addition of water vapor but no impact of increasing the water vapor content has been observed. For silica-forming ceramics, water vapor has an extreme impact on the growth rate and the performance of environmental barrier coatings can be evaluated based on the underlying silica growth rate.
Development of a 250,000 Lb Thrust Bearing Test Rig With Experimental Results
Authors: Wilkes Jason , Omer Farhan Ahmed , Kerr Thomas 
Published: September 2023

Abstract
As the power density of rotating machinery increases, individual component requirements stay the same, while also needing to decrease in size. The design of high-load roller-element thrust bearings involves minimizing the bearing envelope while also maintaining load capacity and life. This paper introduces a new thrust-bearing test rig that uses spherical point loading to deliver up to 250,000 lbf of axial load at speeds up to 60 rpm. This test rig is unique to the literature both in its bearing load and its ability of the rig to test a bearing to the point of failure. The test shaft is spun by a 25 hp motor with a 50:1 speed reducer. The load is applied from a hydraulic pump and a stinger onto a stationary housing. The test rig uses two thrust bearings in a back-to-back arrangement for transferring the applied thrust. The first bearing is the test-bearing, and shaft / housing sleeves allow for a range of sizes and types. The second bearing is a standard tapered roller thrust bearing and is rated for 20 rpm and 1,100 kN (250,000 lbf). A third bearing provides additional radial support to the system. The rig is capable of testing a range of bearing sizes. The bearing housing and shaft use spacers to accommodate bearings from five to eleven inches in diameter, and zero to two inches in length. The rig measures bearing performance through axial displacement and test-bearing drag torque. Water cooling maintains bearing temperature throughout the test. The paper also presents experimental results for a 10-hour test of a new roller element bearing.
Analysis and Prediction of the Machine Capacity Required to Meet Net Zero by 2050
Authors: Wilkes Jason , Reitz Dan , Ransom David , Hofer Doug , Kurz Rainer , Kerr Thomas , Holland Matthew 
Published: September 2023

Abstract
The following paper presents a unique look at the goal of Net Zero 2050, a goal that many of our governments, companies, and citizens support. This paper will focus on the problem from a capacity standpoint. Essentially, there are a number of heat pumps, gas turbines, steam turbines, and the like that will be needed to achieve Net Zero 2050. Many of these machines, systems, and concepts are only in their initial stages of testing and development. This paper will consider a few predicted 2050 power distributions to assess the machinery needed to meet a net zero goal, and then will focus on looking at the capacity of the current machinery market in each sector. These sets of data will then be used in collaboration with historical trends on the adoption of technologies and power block systems, and will determine whether the target for each industry is appropriate, and even possible from a capacity standpoint.
Experimental Investigation of Direct Flame-Cooling Air Interaction With an Effusion Cooled Combustor Wall
Authors: Xavier Pradip , Blaise Antoine , Quevreux Benjamin , Mille Bruno , Pascaud Stéphane , Viguier Christophe , Grisch Frédéric 
Published: September 2023

Abstract
The development of ultra-compact combustors raises challenges regarding wall thermal management. This study aims to understand the behavior of a reacting flow interacting with a cooling air film generated by an effusion wall. Experiments are carried out in an optically-accessible test rig operating at atmospheric pressure, and generating a premixed methane/air turbulent flame. Particle image velocimetry (PIV) and OH planar-laser induced fluorescence (OH-PLIF) are implemented to assess the cold-flow topology and the flame dynamics. Results indicate that an important turbulent flow activity is present in the developing shear layer, being independent of the hole diameter. The air film creates an aspiration of the mainstream. The blowing ratio modifies the flame wrinkling, amplified by the aspiration of the air film. Changing the main equivalence ratio induces a stronger flame-cooling air film interaction. Eventually, a larger hole diameter with a constant wall porosity increases the hole-to-hole distance, enabling the reactive flow to be engulfed at the wall.
Assessment of Fan Stall Point Identification Ability of Steady RANS Computations With the Helicity-Corrected Spalart-Allmaras Turbulence Model
Authors: Yu Zhifan , Raza Hussain , Defoe Jeff 
Published: September 2023

Abstract
Accurate axial fan/compressor stall point prediction using computational fluid dynamics (CFD) has generally been carried out using unsteady computations, often with slowly ramped back pressure. While this approach tends to be accurate with unsteady Reynolds-Averaged Navier Stokes (URANS) computations, it is computationally expensive, often requiring 4–6 rotor blade passages to be included in the computation and necessitating the solution of many rotor revolutions’ worth of flow time. Recently, some work has shown that the helicity-corrected Spalart-Allmaras (HCSA) turbulence model is able, in steady RANS computations, to predict fan stall points within a few percent of experimentally measured operability limits. In this paper, we directly predict stall points by using a steady, multiple reference frame (MRF) or “frozen rotor” approach which employs the HCSA turbulence model. The machine studied is a low-speed axial fan. Computations are carried out using the open-source CFD software package OpenFOAM. The approach is able to predict the stalling flow coefficient to within 0.006 of the experimentally-measured value. Detailed assessments of the flow field at the last stable operating point and at a point just into stall yield show that the HCSA model is able to predict the same stall inception mechanism captured in URANS.
Considerations for Compressible Film Cooling: A Computational Study of the Effects of Transonic Flows and Varying Mainstream Mach Number
Authors: Fox Dale W. , Furgeson Michael , Bogard David G. 
Published: September 2023

Abstract
Recent evidence suggests that film cooling flows with engine realistic mainstream Mach number have declined performance in comparison to those with conventional low-speed laboratory conditions. Consideration and understanding of these effects are fundamental to improving film cooling research. The proposed computational study investigates the film cooling performance of a 7-7-7 shaped film cooling hole with respect to varying mainstream Mach number, with constant Reynolds number. The cases studied include mainstream Mach numbers from 0.15–0.75, with a fixed, engine realistic, hole Reynolds number of Red = 10, 100. Significant results are then evaluated against varying stagnation temperature ratio and blowing ratio. The results showed that at a blowing ratio of 1.75, the adiabatic effectiveness declines significantly with high mainstream Mach number. The decreased performance is due to supersonic flows and shocks in the film cooling hole that disrupt flow in the diffuser section of the hole. These characteristics are observed across all stagnation temperature ratios considered. In addition to these insights, the study discusses the importance of proper thermal scaling and definition of adiabatic effectiveness when operating at high mainstream Mach number. It is demonstrated that the effects of high-speed flow challenge the efficacy of the conventional parameters used to characterize film cooling performance.
Evaluation of Additively Manufactured Heat Exchanger Tubes Using Experimental and Conjugate Heat Transfer Analysis
Authors: Wright Lesley M. , Liu Jong , Kamrath Benjamin , Morris Mark C. 
Published: September 2023

Abstract
Additive manufacturing offers many benefits for the design and production of gas turbine engine components. Direct metal laser sintering (DMLS) expands the available design space while reducing manufacturing cost and cycle time. Engineers continue to explore opportunities for additive components throughout the engine. Generally in regions of reduced stress, heat exchangers provide an opening for immediate implementation of DMLS components. The surfaces of components manufactured using the DMLS process are rough compared to those produced from traditional casting or subtractive manufacturing methods. Therefore, during the design phase, heat transfer designers must understand the heat transfer augmentation and pressure loss increase associated with the roughness from the DMLS process. In this study, DMLS tubes (as printed) were evaluated experimentally. The experimental results were used for validation of a conjugate heat transfer (CHT) model. With the CHT model accurately capturing the roughness effects of the tubes, the model can be confidently extended to other flow conditions and tube configurations. Within the study, a total of six printed tubes were experimentally tested and presented. Four tubes had a diameter of 4.0 mm, and the remaining tubes were 2.0 mm in diameter. The overall lengths of the tubes varied from 180 mm to 230 mm. The coolant flow rate through all tubes varied, yielding Reynolds numbers from 7,500 to 30,000. The overall pressure loss and heat transfer enhancement was measured in the printed tubes. These results were used to validate a CHT model using STAR-CCM+ for the same geometries and flow conditions. The measured Nusselt numbers were 1.25–2.4 times greater than those predicted by Dittus Boelter correlation for heat transfer in a smooth tube. The heat transfer enhancement came at the expense of increased pressure loss compared to smooth tubes. The frictional losses were 1.75–6.5 times greater than those predicted for smooth tubes. The thermofluidic performance of the additively manufactured tubes was generally well predicted by the Norris correlation for rough tubes. The CHT predictions also compare favorably with the Norris correlation. This experimental and numerical study shows the value of printed tubes for heat exchangers. It also highlights the challenges of measuring and predicting the thermal performance for various size tubes.
Experimental Force Coefficients of a Hydrostatic Thrust Bearing and Comparisons to Predictions
Authors: Lim Homin , Ryu Keun 
Published: September 2023

Abstract
Reliable fluid film bearings for high-performance turbomachinery provide significantly extended operating life with controllable stiffness and damping force coefficients at low cost. Hydrostatic thrust bearings support thrust loads and control axial motions. This paper reports measurements and predictions of static and dynamic load characteristics of a hydrostatic thrust bearing fed with pressurized air. The current bearing model uses dynamic axial periodic motion amplitudes, that is models as a function of the initial film thickness, to predict the dynamic force coefficients. Note that, presently, the recorded frequencies and their amplitudes of pneumatic hammer instability along the axial direction are implemented as an external excitation source. The measured and predicted static stiffnesses increase as the film thickness decrease and supply pressure into the bearing increase. The predicted dynamic force coefficients show a favorable agreement with the test data. Analysis reveals the negative damping coefficients and damping ratios as a distinctive onset condition of the present pneumatic hammer instability of the test bearing. A careful recess design and adequate operation conditions along with an accurate prediction can avoid or prevent undesirable pneumatic hammer instability in hydrostatic thrust bearings. The present work extends the knowledge database of hydrostatic thrust bearings with pneumatic hammer instability and provides their design guideline for various operating conditions.
Experimental Investigation of Acoustic Characteristics of Boundary Condition for a Combustor
Authors: Ikwubuo Melvin , Lee Jong Guen 
Published: September 2023

Abstract
In the reported paper, the reflection coefficient at the exit of the bluff-body combustor is experimentally measured over a range of operating conditions for different exit orifice plates without combustion: Ma = 0.05–0.75, the temperature of air = 300K–600K, exit area blockage ratio = 0–69%. A bluff-body combustor similar to an afterburner is used for the measurement. The exit boundary condition is measured without combustion. Measurement results show that the reflection coefficient is significantly complex (i.e., phase is significant) when the flow rate is near or well below Eldridge and Dowling’s criterion. Eldredge and Dowling developed a criterion for the optimum ratio of flow Mach number and perforated liner porosity (ME = σ), such that maximum absorption (i.e., minimum reflection coefficients) of acoustics can be achieved. A model is proposed as a result of the present experimental study that can predict the real part of the reflection coefficient for exit boundary conditions. The acoustic impedance increases linearly as the Mach number increases and decreases with respect to the blockage ratio. The imaginary part of the reflection coefficient at the exit of the orifice plate decreases and approaches zero as the Mach number increases, indicating that the imaginary part of the reflection coefficient may not be ignored for thermoacoustic modeling when the combustor exit is not choked and the Mach number of the flow is lower than 0.35.
Evaluation of the Feasibility of Prediction of Thermoacoustic Instability Using a Wave-Based Reduced Order Network Model for a Micromixer Combustor
Authors: Hunter Riley , Song Jinkwan , Lee Jong Guen 
Published: September 2023

Abstract
The feasibility of prediction of thermoacoustic instability using a wave-based reduced order network model is evaluated for a micromixer combustor where the flame length is about 43% of the combustor length. A wave-based reduced order network model using a linear acoustic theory is formulated in such a way that the impact of various modeling input parameters such as non-compactness of flame, temperature distribution in the combustor and acoustic boundary conditions on the prediction of onset of combustion dynamics and instability frequency be evaluated. Both global and local flame transfer functions are experimentally determined and incorporated in the network model as the source terms to determine if the compact flame assumption is valid for the prediction. The acoustic boundary conditions as well as the actual temperature distribution are experimentally measured. Modeling results with the global or the local flame transfer function as the source term and with the measured flame temperature show that the prediction of the combustion dynamics does not agree with the experimental results when the analytically modeled boundary conditions are used, warranting the correct determination of acoustic boundary conditions in order to predict the onset of instability correctly. Also, the implementation of distributed flame in the model enhances the accuracy of prediction of thermoacoustic instability for the flame presented in this study.
ICME Simulation of APS Process and Damage in Ceramic Coatings
Authors: Marrey Mallikharjun , Huang Dade , Morscher Gregory N. , Miraj Rashid , Abdi Frank , Ballant Daniel , Jefferson George , Panakarjupally Ragavendra P. 
Published: September 2023

Abstract
This work shows an enhanced Integrated Computational Material Engineering (ICME) method for modeling of multi-material coating of Air Plasma Spray (APS) Ceramic Coating Process. ICME simulation of the APS process includes defects and the effect of defects (bending, curvature, delamination, and cracks), in-service analysis under Burner-Rig and furnace thermal loading conditions, and the effect of high temperature on Thermal Barrier Coatings (TBC) over the metallic substrate of dog bone specimens to demonstrate durability and damage tolerance (D&DT).
To achieve this end, a multi-physics-based ICME methodology and virtual design of experiment (DOE) tools are developed to virtually generate multi-layered materials including high-temperature coatings for use in engine/aircraft high-temperature exhaust regions. The ICME innovation centers around: 1) Thermo-Physics Modeling (plasma, vapor, liquid, solid) to predict the material’s thermal profile, voids, densities, and thermal conductivities; 2) Multiscale Material Modeling of the top coat, bond coat, and substrate to predict material performance: a) temperature-dependent strength, stiffness, residual stresses and strains considering the effect of defects, and b) rumpling, surface waviness, and Thermal Growth Oxidation (TGO); 3) Structural Analysis and D&DT to predict coating and substrate failure evolution (i.e., delamination, oxidation, etc.) during thermo-mechanical in-service loading; and 4) Simulation of residual stress/strains due APS process. The simulation also shows rumpling and TGO growth have little effect on the as-built APS TBC specimen.
Verification was performed using test data on TBC/Haynes230 systems under thermal loading. Tests and predictions were in close agreement. Both test and prediction showed an as-built specimen exhibiting bending during APS process and delamination during Burner-Rig testing.
Identification of Dynamic Force Coefficients for an Additively Manufactured Hermetic Squeeze Film Bearing Support Damper Utilizing a Pass-Through Channel
Authors: Ertas Bugra , Gary Keith , Adcock Tom 
Published: September 2023

Abstract
The following paper presents breakthrough experimental results for a new hermetic squeeze film damper (HSFD) concept that is integrally designed within an externally pressurized tilting-pad radial gas bearing support. The flexibly damped gas bearing module was designed for a 7.2” (183 mm) diameter shaft and fabricated using direct metal laser melting (DMLM); also known as additive manufacturing. The bearing and HSFD were sized based on ongoing studies for oil-free super-critical carbon dioxide (sCO2) power turbines in the 8.5MW-10MW power range. The development of the new damper concept was motivated by past dynamic testing on HSFD, which generated frequency dependent stiffness and damping force coefficients. In efforts to eliminate the frequency dependency, a new HSFD architecture was conceived that adds accumulator volumes and a pass-through channel to previously conceived HSFD flow network designs. The other motivation of the work is the need for developing a cost-effective and reliable oil-free bearing technology that is scalable to large power turbomachinery applications. There were several objectives to the following work. The first objective was to successfully design and fabricate a single piece bearing-damper using additive manufacturing, while dimensionally controlling critical design features. The paper discusses the manufacturing steps and shows cut-ups that reveal adequate clearance control capability with internal damper clearances. The second objective was to perform experimental testing with the new HSFD design in efforts to extract stiffness and damping coefficients for excitation frequencies within 20–160 Hz and peak vibration amplitudes between 0.25 mils (6.35 microns) to 1mil (25.4 microns). The test results for a single HSFD bearing module indicated that the design modifications to the HSFD architecture were successful in eliminating nearly all the frequency dependency for the stiffness force coefficient. The dynamic tests yielded a stiffness coefficient that varied between 112 klb/in (19.6 MN/m) and 96 klb/in (16.8 MN/m). The damping force coefficient however, exhibited relatively more variation with frequency with values residing between 175 lb-s/in (31 kN-s/m) to 214 lb-s/in (37 kNs/m). Finally, the paper advances a three-dimensional fluid-structure interaction (FSI) model using transient finite element analysis (FEA) coupled to a computational fluid dynamics (CFD) model. The FSI analysis performed between 20Hz-80Hz was used to predict the stiffness and damping of the HSFD using a quarter section model of the damper. The FSI analysis was able to support test results by showing only a 6–7.4% change in the magnitude of force coefficients. Stiffness predictions agree reasonably well with experiments whereas damping is underpredicted.
Overall Cooling Effectiveness With Internal Serpentine Channels and Optimized Film Cooling Holes
Authors: Yoon Christopher , Flachs Elise M. , Ellinger Molly R. , Bogard David G. 
Published: September 2023

Abstract
The overall cooling effectiveness for gas turbine airfoils is a function of the combined cooling due to internal cooling configurations and film cooling configurations. Typically, film cooling configurations are evaluated independent of the cooling effects of the internal feed channels, generally based on adiabatic effectiveness measurements. In this study, we consider the coupled effects of internal cooling and film cooling configurations through measurements of overall cooling effectiveness for film cooling holes fed by a coflow/counterflow channel and a serpentine channel. A film cooling hole designed by adjoint optimization techniques (X-AOpt) is compared to a standard shaped hole with 7° forward and lateral expansions (7-7-7 SI). Experiments without film cooling showed that the serpentine channel had 35% to 50% greater overall cooling effectiveness than the straight, coflow channel. Experiments with the X-AOpt hole combined with a serpentine channel showed an area-averaged overall cooling effectiveness of ϕ̿, which was a 70% increase compared to the overall cooling effectiveness of the serpentine channel without film cooling. When the X-AOpt hole was fed with a coflow channel with similar coolant mass flow rate, the overall cooling effectiveness was ϕ̿=0.44, i.e. 30% lower than when using the serpentine channel. Interestingly, adiabatic effectiveness measurements with the X-AOpt holes showed a more uniform hole-to-hole performance when using the serpentine channel compared to the coflow channel.