bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Measurements and CFD Predictions of NOx Emissions From a Water-Cooled Rotating Detonation Engine
Authors: Strakey Peter A. , Ferguson Donald H. 
Published: September 2023

Abstract
A water-cooled Rotating Detonation Combustor (RDC) operating on hydrogen and air and utilizing a pintle-style injector with an axial air flow path was operated over a wide range of mass flowrates, equivalence ratios and back-pressures producing a variety of wave modes. Measurements of NOx as well as O2 were conducted by sampling the combustor exhaust just downstream of the throat after the combustor reached a thermally steady-state condition.
2D RDC simulations were conducted with several detailed hydrogen-air chemical mechanisms along with detailed NO formation chemistry to investigate the sensitivity of the results to the chemical mechanisms as well as to derive a better understanding of where in the detonation wave NO is being formed.
3D simulations using a Large Eddy Simulation approach with a Partially Stirred Reactor model were conducted and validated against the experimental data. Wall heat losses were included and validated against global wall heat losses measured in the water-cooled RDC. While the simulations generally predicted higher NOx emissions than what was measured, the trends with equivalence ratio were well predicted.
The implications of this study are that NOx emissions from RDCs are not unreasonably high and CFD can be used to predict NOx emissions as well as to optimize injector geometry. Selection of an appropriate NOx chemistry sub-model along with experimental validation is key to improving the reliability on the simulations.
A Surge/Stall-Capable Dynamic Performance Simulation Methodology for a Turbojet Engine
Authors: Güllü Emrah , Aran Gökhan 
Published: September 2023

Abstract
A lumped-parameter dynamic performance model for a single-spool turbojet engine is presented in this paper. This model can handle pre and post-stall transients under forward and reverse-flow conditions. The inter-component volume technique is employed instead of the standard matching technique to be able to handle high-frequency transients and reverse-flow conditions. Inspired by Greitzer’s lumped-parameter surge model, momentum (duct) and volume elements are placed within the flow path to handle surge dynamics. Compressor and turbine maps are extended to low-flow and reverse-flow regions using a combination of the guidelines presented by Kurzke, the cubic axisymmetric characteristics of Moore and Greitzer, and a quadratic function guess for in-stall characteristics. Combustor efficiency, stability limits, and delay are taken from the literature. Post-stall behavior of the model is validated using the data available in the literature for a Rolls-Royce Viper engine. A good match is observed with a correct prediction of post-stall behaviors which transition from surge after locked stall to multiple surge cycles around 80% speed and multiple surge cycles to surge after flame-out around 95% speed. The effects of different modeling choices and modeling parameters on the obtained results are discussed. The produced model can be calibrated for a specific engine with surge tests and it can be used for hard-to-test scenarios like surge after shaft breakage. Different surge/stall-causing events, such as fuel spiking, in-bleeding, transient inlet distortion, and shaft breakage, are simulated to see the capabilities of the model.
Development of a Turbocharger Speed Sensor Using Fiber Optic Coupled Optical Method
Authors: Kang Sang-Guk , Pope Aaron J. , Schroen Erik S. , Kruger Kurt M. , Kim Kenneth S. , Kweon Chol-Bum M. , Micka Daniel J. , Finger William , Gibson Joseph A. , Meininger Rik D. , Musser Marshall R. 
Published: September 2023

Abstract
Turbochargers play a key role in producing more power for internal combustion engines of small aircrafts operated at altitudes with low air density. However, turbochargers can experience catastrophic failure at specific operating conditions where aeroelastic instability or resonance occurs at extremely high speed, putting the aircrafts at high risk. Therefore, it is critical to avoid turbocharger shaft speeds at these dangerous conditions, requiring accurate and stable turbocharger speed measurements. Currently, turbocharger speed sensors such as eddy-current sensors based on electromagnetic fields are often used for this purpose. However, these devices have limited capabilities such as applicable impeller blade material, maximum measurable speed, and small mounting distance between the sensor and impeller blade. Therefore, the present study focuses on development of a new turbocharger speed measurement method using a Fiber Optic Coupled Optical Speed (FOCOS) sensor and assessment of its capabilities. The FOCOS sensor was installed in the compressor housing of a high-speed turbocharger mounted on an internal combustion engine subjected to altitude conditions. These results were also compared to the performance of eddy-current speed sensors. It was concluded that the FOCOS sensor reliably measured turbocharger speeds over 250 kRPM for a range of impeller blade materials including aluminum and titanium, while the eddy-current speed sensor showed significant limitations.
Coupled Lateral-Torsional Analysis With Structural Interaction on Geared Shaft
Authors: Libraschi Mirko , Capanni Francesco , Innaco Luca , Rossin Stefano 
Published: September 2023

Abstract
In the theoretical framework of rotordynamic predictability, Baker Hughes has developed several validations of lateral torsional dynamic modeling. The train under study is a geared turbogenerator shaft line system that consists of a generator mounted on a baseplate and connected with a planetary reducer directly supported (overhung) on the generator frame. The gas turbine driver is not included in the modeling due to the use of a diaphragm flexible coupling connecting it with the reducer. The shaft line in object is then only composed by the planetary gear (four stars) rigid connected with a generator solid poles rotor (four poles) observed during mechanical running test (no load condition). The presence of the gearbox prevents lateral and torsional vibrations from being treated independently. Furthermore, the interaction of the rotordynamic system with its supports (machine frames, bearing housings and baseplate) is described using state space matrices approach. This modeling methodology is resulted very likelihood in predicting the dynamic system natural frequencies as well as peak level of reached vibration in all analyzed speed range. Operational modal analysis has been used to compare expected natural frequencies vs identified ones while the level of vibrations is induced by applying unbalance force in the proper location (i.e. shop test verification).
Hydrogen and Ammonia Blending With Natural Gas: Ignition Delay Times and Chemical Kinetic Model Validation at Gas Turbine Relevant Conditions
Authors: Pierro Michael , Urso Justin , Rahman Ramees K. , Dennis Christopher , Albright Marley , McGaunn Jonathan , Kinney Cory , Vasu Subith S. 
Published: September 2023

Abstract
Ignition delay times from undiluted mixtures of natural gas (NG)/H2/Air and NG/NH3/Air were measured using a high-pressure shock tube at the University of Central Florida. The combustion temperatures were experimentally tested between 1000–1500 K near a constant pressure of 25 bar. As mentioned, mixtures were kept undiluted to replicate the same chemistry pathways seen in gas turbine combustion chambers. Recorded combustion pressures exceeded 200 bar due to the large energy release, hence why these were performed at the high-pressure shock tube facility. The data is compared to the predictions of the NUIGMech 1.1 mechanism for chemical kinetic model validation and refinement. An exceptional agreement was shown for stoichiometric conditions in all cases but strayed at lean and rich equivalence ratios, especially in the lower temperature regime of H2 addition and all temperature ranges of the baseline NG mixture. Hydrogen addition also decreased ignition delay times by nearly 90%, while NH3 fuel addition made no noticeable difference in ignition time. NG/NH3 exhibited similar chemistry to pure NG under the same conditions, which is shown in a sensitivity analysis. The reaction CH3 + O2 = CH3O + O is identified and suggested as a possible modification target to improve model performance. Increasing the robustness of chemical kinetic models via experimental validation will directly aid in designing next-generation combustion chambers for use in gas turbines, which in turn will greatly lower global emissions and reduce greenhouse effects.
Tilting Pad Journal Bearing CFD Parametric Modeling for New Energy Transition Challenges
Authors: Gheller Edoardo , Reddy Vishnu Vardhan , Koyyalamudi Satish , Chatterton Steven , Panara Daniele , Pennacchi Paolo 
Published: September 2023

Abstract
The necessity of increasing the efficiency and reducing the carbon foot-print of machines is pushing centrifugal compressor bearings design to higher and higher peripheral speed and lower oil consumptions especially in the new energy transition fields, resulting in an increase in the bearing temperatures. Therefore, the bearing thermal management starts to play a major role in extending the machine operability and reducing the maintenance frequency. A full three-dimensional (3D) parametric conjugate heat transfer Computational Fluid Dynamic (CFD) model for Tilting Pad Journal Bearings (TPJBs) is introduced in this paper to address the temperature aspects of oil-film bearings. The parametric geometry of the model and the automatic mesh update, allow the equilibrium position search to be obtained without adopting any dynamic mesh algorithms. The tilting pad and rotating shaft equilibrium position is automatically calculated with a Newton-Raphson algorithm. The static performance of the TPJB is investigated for different journal diameters, bearing clearance, and operating conditions. The numerical results obtained are compared with experimental data from Compressor Mechanical Running Tests to demonstrate the reliability of the model presented. The 3D distributions of the oil pressure, velocity and temperature given by the CFD model, can be locally optimized to face the new energy transition challenges.
Integrated CFD-FEA Acoustics Workflow for Tonal Fan Noise Simulation: Far-Field Propagation and Design Impact Analysis
Authors: Pluchart Sylvain , Braun René 
Published: September 2023

Abstract
For numerous applications, mitigation of ducted fans noise emission is a major design challenge. In the context of aircraft propulsion for example, certification standards have become more stringent over the last decades to support sustainable and environmentally protecting mobility solutions. With current design practices, many physical tests on stationary rigs or during fly-over tests are still required to fulfill all design requirements. Numerical methods have the potential to improve that process by reducing the time and the cost to assess design variants. To be effectively deployed within the industry, these methods must be able to capture the major physical phenomena while offering a competitive computational cost. With this objective in mind, this paper introduces a simulation methodology to predict the tonal fan noise resulting from the rotor-stator interaction and its propagation to the far field environment. With an application to an existing fan design, this paper shows how the workflow establishes a fast and efficient analysis process, by connecting CAD modeling, CFD and FEA simulations in a modular way. Focus will be put on the harmonic balance methodology for CFD simulation of the noise generation, and on the FEMAO methodology for acoustic noise propagation. Results shows a drastic reduction in turnaround time compared to conventional CFD and FEA methods, allowing the entire workflow to be set up and executed within a day of engineering time on an individual workstation.
Laser Welding in Steam Turbine Rotor Recondition
Authors: Chaopanich Isarawit , Buapoon Jitti , Preebut Vissaruud , Nararak Arpaporn 
Published: September 2023

Abstract
The recondition project of the steam turbine rotor with power output of 16 MW aimed to apply laser welding technic in building up filler material on the damaged journal areas at which scratches and cracks were observed by liquid penetrant and magnetic particle testing. Machining work was performed on the lathe in order to remove damages, and additive laser welding with the 1.20Cr-0.5Mo filler wire was carried out with the controlled parameters on the two journal areas. The vertical heat treatment and final machining on the weldments of the rotor were consecutively completed to achieve final size diameters with a deviation of 0.02 mm [0.0008″] and surface roughness of 0.3 μm [1.18 × 10−7″] The results of this refurbishment process by using the low heat dissipation laser welding illustrated that no indications were observed on the welded areas with the acceptable maximum hardness of 334 HV0.3. The maximum residual stresses on the specified areas and the total rotor length were reported before and after repair −314.2 MPa [−45.57 ksi], −320.0 MPa [−46.41 ksi] in compression, and 4,570.718 mm [179.949″], 4,570.749 mm [179.951″], respectively. The final maximum radial run out of the rotor was 0.05 mm [0.0020″] lower than that of the incoming condition of 0.07 mm [0.0028″]. After low-speed balancing, the maximum rotor mass unbalance was 13.0 g [0.029 lbs] not exceeding the acceptance criteria of the quality grade G1 31.2 g [0.0687 lbs]. In consequence, the rotor was operated again without vibration problems.
Open NASA Blade Models for Nonlinear Dynamics Simulations
Authors: Kojtych Solène , Batailly Alain 
Published: September 2023

Abstract
This contribution presents a catalogue of open turbomachinery blade models dedicated to nonlinear dynamics simulations. Based on a specifically developed in-house computer code, 3D CAD models and finite element models of multiple-circular-arc NASA airfoils are generated. Both the in-house code and the models are made freely accessible online. To cover a wide range of geometries, 39 blades are considered from different stages and with different aspect ratios. It is expected that this blade catalogue will provide an opportunity for the direct comparison of recently developed methodologies relative to nonlinear vibration phenomena in turbomachines, including rubbing events and blade-tip/casing contacts. To this end, the paper also contains original results for some of the most emblematic NASA blades, with an emphasis on nonlinear interaction maps and a detailed presentation of redesign operations to mitigate high amplitude of vibrations when blade-tip/casing contacts occur.
Consideration of Non-Ideal Detonation Regimes Influenced by Wave Modes in a Water-Cooled Rotating Detonation Engine Using OH* Chemiluminescence
Authors: Johnson Kristyn B. , Ferguson Donald H. , Weber Justin M. , Nix Andrew C. 
Published: September 2023

Abstract
Although inherently unstable, existing research in rotating detonation combustion supports its application in notionally steady processes resulting in greater availability compared to conventional, constant pressure combustion. Further improvements rely on a more in-depth understanding of system losses and identifying conditions which optimize device performance. Within this study, the presence and proportion of ideal and non-ideal combustion regimes is compared across a variety of process conditions and wave modes. Large-scale data analysis seeks to summarize proportional heat release associated with commensal, parasitic, and detonative combustion averaged across individual traces of OH* chemiluminescent data acquired at the detonation plane. Means of regime partitioning based on the anatomy of the time-resolved OH* signal are proposed to ensure consistent analysis throughout the current and future studies concerning combustion regimes. Of particular interest is the possible influence of wave on the non-ideal combustion in relative proportion to the desired detonation. Results showed improved percent detonation with increasing significance for the following trends: decreasing equivalence ratio, increasing wave count, decreasing wave velocity, and increasing detonation time. Increased wave number, brought on by decreased equivalence ratios and wave velocities, is thought to decrease fill region surface area, and therefore, decrease non-ideal contact burning. Additional analysis is performed to consider possible trend variation due to the presence of stable galloping waves, which were found to have minimal influence on relative percent detonation values. The outcome of this study suggests operational states which correspond to increased wave quantities for increased proportions of reactants consumed by the targeted detonative combustion regime.
Ceramic and Metal Additive Manufacturing of Monolithic Rotors From SiAlON and Inconel and Comparison of Aerodynamic Performance for 300W Scale Microturbines
Authors: Badum Lukas , Prochaska Thomas , Schwentenwein Martin , Cukurel Beni 
Published: September 2023

Abstract
The gas turbine industry is continuously developing and testing new materials and manufacturing methods to improve the performance and durability of hot section components, which are subjected to extreme conditions. SiAlON and Inconel 718 are especially desirable for turbomachinery applications due to their high strength and high temperature capabilities. To demonstrate the viability of additive manufacturing for small scale turbomachinery for 300W scale microturbines, a monolithic rotor with a design speed of 450,000 RPM containing radial turbine and compressor was developed considering additive manufacturing constraints. The geometry was manufactured from SiAlON and Inconel 718 using lithographic ceramic manufacturing and selective laser melting, respectively. The additive manufacturing and thermal process parameters as well as material characterization are described in detail. Surface and computerized tomography scans were conducted for both rotors. While the metallic rotor showed undesirable printing artefacts and a large number of defects, the ceramic part achieved a level of relative precision and surface quality similar to large-scale production via casting. To compare turbomachinery performance, an aerodynamic test facility was developed allowing to measure pressure ratios and efficiency of small compressors. The rotors were tested in engine realistic speeds, achieving a compressor rotor pressure ratio of 2.2. The ceramic part showed superior efficiency and pressure ratio compared to the Inconel rotor. This can be explained with lower profile and incidence losses due to a higher fidelity physical representation of the model geometry and better surface finish.
Thermochemical/Thermomechanical Synergies in High-Temperature Solid Particle Erosion of CMAS-Exposed EBCs
Authors: Stokes Jamesa L. , Presby Michael J. , Webster Rebekah I. , Setlock John , Harder Bryan J. 
Published: September 2023

Abstract
Environmental barrier coatings (EBCs) are an enabling technology for the use of SiC-based ceramic matrix composites in next generation gas turbine engines. In the extreme engine environment, EBCs must be able to withstand a variety of individual damage mechanisms and their interactions with each other. Ingested particulates/debris can cause both thermochemical and thermomechanical degradation of EBCs. Siliceous debris primarily based on calcium magnesium aluminosilicates (CMAS) can melt and infiltrate and/or react with EBCs above 1200°C. Similarly, ingested debris can lead to mechanical damage and recession of coatings due to particulate erosion. Both modes of degradation can occur simultaneously during engine operation, and it is crucial to comprehensively understand the mechanisms of coating failure due to high-temperature particulate interactions. This study assesses the erosion durability of Yb2Si2O7-based EBCs exposed to CMAS of various loads in NASA Glenn’s Erosion Burner Rig Facility. CMAS exposures and erosion testing were carried out at 1316°C. The effects of CMAS loading and exposure time on EBC erosion durability were evaluated using Al2O3 as an erodent material.
Modelling of Two-Phase Water Ejector in Rankine Cycle High Temperature Heat Pumps
Authors: Abu Khass Omar , Tran Anh Phong , Klöppel Steffen , Stathopoulos Panagiotis 
Published: September 2023

Abstract
Industrial high temperature heat pumps (HTHPs) can provide carbon-free process heat when operated with renewable energy sources. Using water as the working medium greatly increases the possible range of operation without the detrimental effects of traditional working fluids. One main challenge with this type of heat pump is the high compression ratio required to achieve a given temperature lift. As a result, water based heat pumps need several compression stages. Furthermore, the steam leaving the compressor is highly superheated. Ejectors driven by high pressure condensate allow to de-superheat the steam from the compressor outlet while simultaneously increasing its pressure. Thereby, the required power for compression as well as the number of compression stages can be reduced. This paper studies how the implementation of the two-phase water ejector influences the thermodynamic performance of Rankine cycle HTHP using a thermodynamic model of the ejector. Several cycle architectures are developed to study the ejector integration in the heat pump cycle, including traditional single-stage and multi-stage cycles. The cycles studies are conducted in the Modelica language, in the Modelon Impact environment. The study aims at informing about new developments in two-phase water ejectors and their application potential in Rankine cycle HTHPs. First simulations suggest an efficiency improvement of about 10% through the use of an ejector in the heat pump cycle.
Investigation of the Aerodynamic Interaction Between Rotor and Second Stator in the Large Scale Turbine Rig
Authors: Linne Marius , Ade Dominik , Eitenmüller Johannes , Leichtfuß Sebastian , Schiffer Heinz-Peter , Lyko Christoph , Schmid Gregor 
Published: September 2023

Abstract
This paper presents the results of an investigation of two different interface modeling approaches for Computational Fluid Dynamics in turbomachinery and their influence on the second stator aerodynamics in the 1.5-stage Large Scale Turbine Rig. Highly accurate five-hole probe data as well as oil flow visualizations are used to investigate the aerodynamics within the second stator passage and to validate the numerical results. While unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations appear to be a better qualitative representation of the second stator aerodynamic experiments, the steady-state (RANS) simulation predicts a turbine efficiency that is closer to the experimental data. In both approaches, the boundary conditions, computational domain and turbulence parameters are kept the same. The key difference between the two simulations is the resolution of time and hence unsteady effects. The RANS approach uses a Mixing-Plane interface between stationary and rotating reference frames. Here, unsteady effects of blade row interaction are neglected by mixing flow quantities in the circumferential direction. This affects the development and propagation of the vortex system in the downstream blade row. To account for effects of rotor-stator-interaction and reduce modeling errors, more expensive unsteady simulations are used. In the rotor exit plane, the URANS simulation shows a better match with experimental data, which theoretically should be the more accurate inlet condition for the downstream second stator. Here, unsteady interactions between the vortex systems of the rotor and the second stator lead to an overprediction of the losses in the second stator passage in the URANS compared to the RANS case. Therefore, the overall efficiency is more accurately predicted by RANS.