bluuebunny/crossref_metadata_2025 huggingface dataset:
Large Eddy Simulation of Hydrogen Flame Stabilization in a Reheat Gas Turbine Combustor
Authors: Cartwright Ethan , Xu Chao
Published: September 2023

Reheat gas turbine combustors utilizing high hydrogen content fuel blends serve as a potentially effective low-emission alternative energy system; however, these combustors operate under unique conditions that lack low-cost models for accurately predicting flame stabilization. A large eddy simulation (LES) with detailed chemistry and adaptive mesh refinement is performed on a simplified geometry of the Ansaldo GT36 sequential combustor with an elevated inlet temperature and vitiated air-hydrogen flow in a rectangular mixing duct and combustion chamber, a configuration previously modeled with direct numerical simulation (DNS) in ref. [15]. Flame characteristics and stabilization are investigated, finding similarity in stabilization mechanism and location, but discrepancies in flame front shape and size as compared to DNS results — likely due to a combination of a reduced flame speed fuel composition from that used in DNS results and too coarse a grid for the highly reactive hydrogen fuel. Various wall treatments are investigated, finding indistinguishable behavior across heat transfer models for Law of Walls models, reduced heat transfer with an isothermal wall indicating unresolved length scales, and expected high near wall temperatures for adiabatic wall. The latter two causing significant differences in flame stabilization location and mechanism as compared to DNS results. Results gathered here validate the feasibility of stabilized sequential combustor LES models which can complement fundamental experimental and DNS results in their application to the design process, though further improvements to the LES model are needed before it can be applied to systematic flame characteristic analysis.
Aircraft Engine Performance Augmented by Wet Compression
Authors: Gkoutzamanis Vasilis G. , Psaropoulos Michalis K. , Kalfas Anestis I.
Published: September 2023

This work presents a systematic thermodynamic study to identify and assess the effects of wet compression stage conditioning in aeroengines. Similar techniques found in the literature are initially reviewed. The performance of a modern two-spool turbofan engine variant is then modelled. To account for the humidification effects, a 0D evaporation model is developed and three fluids (water, jet fuel and liquid hydrogen) are evaluated. The results verify that earlier injection is more effective per mass injected, if water is used. However, upstream injection is limited by the amount of water that can be absorbed from the air stream. If jet fuel is used, injection is not feasible for the conditions studied and is overall limited by its autoignition and solidification temperatures. Hydrogen injection indicates that it may facilitate several valid injection points, at low quantities. A further error propagation analysis is made, to evaluate the model’s sensitivity in ambient conditions. Overall, a comparison of the three fluids indicates hydrogen’s feasibility (up to 15% ΔThrust and −35% for EINOx as compared to water’s up to 12.5% ΔThrust, −28% EINOx for similar injection levels) as compared to the other two fluids.
Stability of a Lateral Contact Between a Rotor and Stator When Rubbing
Authors: Wilkes Jason
Published: September 2023

In many rotating machines, close clearances between a rotor and stator at seals, bearings, and other locations may result in contact between the rotor and stator. The current work investigates a contact phenomenon that can occur in these instances that can become unstable. The contact model is applied to a simple overhung rotor similar to an eye seal on an integrally geared compressor. A stability analysis is presented to determine the threshold speed of instability of the rotor in contact with a stator.

It was determined that a correlation between the change in real part of the eigenvalue with respect to rotor speed exists and is proportional to the coefficient of friction at the rub location. The resulting onset speed of instability is determined through an analytical solution to the real part of the eigenvalue when rotor speed and is zero and contact forces are present. It is interesting, however, that the contact stiffness and damping have no affect on rotordynamic stability of the tool. The analysis was tested by comparison with eigenvalue analysis performed in XLTRC2. The results of the comparison showed that the analytical prediction was accurate to within one percent of the true threshold speed of instability.
Test Rig Concept for Evaluating the Performance of a CO2 Immersed Electromechanical Rotor System Utilizing Gas Bearings: Part-2 Thermal Systems & Flow Loop Design
Authors: Bidkar Rahul A. , Kumar Uttara , Zhang Xiaohua , Sarawate Neelesh , Powers John , Anandika Nevin M. , Ertas Bugra
Published: September 2023

Closed-loop supercritical carbon dioxide (sCO2) power cycles and sCO2 turbomachinery hold promise for waste-heat recovery (WHR) in natural gas (NG) pipeline compression stations. A companion paper [2] develops a cascaded sCO2 thermodynamic cycle (operating between 237 bara, 485 °C and 85 bara, 35 °C) using a two-train hermetically sealed turbomachinery power system as a concept for a WHR bottoming cycle at NG compression stations. The key novelty of the hermetic sCO2 turbomachinery was the inclusion of CO2-immersed gas bearings and a CO2-immersed direct-drive permanent magnet (PM) electric machine, both operating in a high-pressure CO2 environment of 27.6 bara. Operation of immersed gas bearings and the immersed PM electric machine in a high-speed, high-pressure CO2 environment is expected to result in high levels of windage heat generation — that can cause undesired structural distortions in thin-film gas bearings, resulting in compromised load carrying capability. Furthermore, high temperature from the windage heat can lead to structural stresses, loss of stator winding laminate glue and overall deterioration of the electric machine performance. To mitigate these risks experimentally, a companion paper [10] proposes a high-speed hermetically sealed test rig that simulates a highspeed 27krpm rotor supported with three radial gas bearings and a thrust gas bearing. High-pressure CO2 is supplied to the test rig with a Gas Supply Flow Loop that includes gas boosters, regulators, flow meters and chillers for a steady state operation. This paper discusses the thermal analysis model for the test rig. Specifically, as part of the thermal model, we present an ASPEN HYSYS model of the external flow loop that tracks the thermodynamic state of the CO2 gas supplied to the rig. Internal to the rig, the thermal model consists of a fluid-advection network that is thermally coupled with a steady-state thermal conduction solver to predict the windage heat, heat transfer coefficients, metal and fluid temperatures in the rig. The internal fluid advection network uses simple 1D fluid elements and real-gas CO2 properties for internal rig flows as well as commercial CFD software for modeling complex thin-film flows in gas bearings. The thermal model uses the principle of energy conservation to couple the heat flow in the advection network with the surrounding rig structural/rotating parts. The thermal model was implemented using an in-house solver using ANSYS workbench and ANSYS APDL script as the underlying platform. We present baseline temperature predictions for the test rig and quantify the amount of cooling mass flow needed to operate the test rig with its temperature constraints. We study the role of cooling in enabling reliable operation of the gas bearing system and electric machine at various rig internal pressures.
Comparison of Computational Predictions for a Cooled High-Pressure Turbine to Data From a Short Duration Experiment
Authors: Christensen Louis , Celestina Richard , Sperling Spencer , Mathison Randall , Aksoy Hakan , Liu Jong , Nickol Jeremy
Published: September 2023

Cooling of hot gas components is essential to the operation of modern gas turbine engines. To continually improve designs and deploy the next generation of cooling, experimental and predictive capabilities must increase as well to more accurately understand new designs. One region of interest is the squealer tip of the high-pressure turbine blades which encounter high thermal loading. This work will investigate the performance of the film cooling in the squealer tip using both experimental data collected with a high-speed infrared camera as a part of a previously published work and transient conjugate heat transfer simulations of the blade passage.

This work investigates the comparison between the experimental data and numerical predictions. Verification of the conjugate heat transfer model is done by examining the mass flowrate through the passage, pressure and thermal loading on the blade midspan, and temperature distributions on the blade tip. In depth analysis of the spatial temperature distributions on the blade tip is conducted as well. From this work, it can be seen that the infrared measurement system is capable of capturing low spatial frequency temperature distributions with good agreement to the computational predictions. Additionally, the numerical predictions are compared to other simulations of the same blade passage which highlight the ability of conjugate heat transfer analysis to capture the heating of the blade during the experiments further improving predictive capabilities.
Modeling Tip Flow Structures and Heat Transfer in Contemporary Cooled and Uncooled High-Pressure Turbine Blades
Authors: Christensen Louis , Celestina Richard , Sperling Spencer , Mathison Randall , Aksoy Hakan , Liu Jong , Nickol Jeremy
Published: September 2023

Cooling the squealer blade tips is essential to ensure efficient operation of gas turbine engines. The squealer tip reduces tip leakage flows but it is subject to high levels of thermal loading due to the difficulty in cooling the extended surface. Other studies have identified the dominate flow structures in the squealer blade tips namely the scraping vortex formed due to the relative motion of the turbine shroud and the pressure cavity vortex which forms from flow leaking over the pressure side squealer rim. These vortices influence the tip leakage flowrate across the blade tip, impingement on the squealer cavity floor, and the thermal loading on the squealer rim & cavity floor. Cooling jets can be used to modify these flow structures to reduce the thermal loading on the blade tips.

This work investigates how the tip flow structures are changed when cooling is introduced to the turbine blade. Transient conjugate heat transfer simulations of a turbine passage are run utilizing a solid uncooled turbine blade and a fully cooled high-pressure turbine blade with a contemporary tip cooling scheme. The large leading edge cooling hole disrupts the formation of the scraping vortex and pressure cavity vortex significantly changing the flow structures and thermal loading on the remainder of the cavity. Smaller cooling holes along the blade tip alter the position of the tip vortex structures which can be beneficial or detrimental to the local heat transfer loading. This analysis shows that cooling jets can affect the thermal loading by changing the flow structures within the tip in addition to creating a layer of protective cooling gas.
Turbomachinery for Laboratory-Scale Demonstration of Pumped Thermal Energy Storage System
Authors: Rimpel Aaron , Just Joshua , Smith Natalie
Published: September 2023

Long-duration, grid-scale energy storage technologies provide a potential pathway to enable full penetration of renewables on the electricity grid and still maintain grid reliability and security. One approach is to use a pumped thermal energy storage (PTES) system, which is charged by using a heat pump (consumes electrical energy) to raise the temperature of a warm medium while lowering the temperature of a cool medium, creating hot and cold media stores, respectively. The PTES system is discharged by using a heat engine (produces electrical energy), which is the reverse of the charge cycle. PTES is a promising technology that offers high potential system performance, implementation versatility, no geological or geographical constraints, and leverages many existing component technologies. However, no such air-based system has been built and demonstrated at any scale, which is necessary for validation and eventual commercialization.

This paper describes the development of turbomachinery for a first-of-a-kind demonstration of a PTES system. At the kilowatt scale, no off-the-shelf machinery exists to meet all performance and operability requirements, so custom turbomachines were required — one for the charge (heat pump) cycle and one for the discharge (heat engine) cycle. Each machine comprises a compressor, turbine, and a motor/generator that has an operating speed range up to 55,000 rpm. The scope of this paper focuses on the design of the turbomachines, including description of the machine performance requirements, bearing and damper designs, rotordynamics, mechanical design, manufacturing, assembly, and commissioning activities.
Aeroacoustic Effects on the Forcing of Fan and Compressor Blades Due to Distortion
Authors: Mårtensson Hans , Billson Mattias
Published: September 2023

A distorted air stream entering an aeroengine fan or compressor leads to harmonic forces on the rotating blades. These aerodynamically induced forces are well known causes for blade vibration and associated fatigue problems. Significant levels of distortion can arise from different sources like side wind and high angles of attack that normally occur at specific operating conditions. For aircraft with the engine closely integrated with the fuselage the engine will be exposed to distortion during the entire flight cycle. This increases the risk of operating in conditions where blade resonances are excited. The sensitivity to the forcing is also accentuated in this case as the exposure over time gives a large number of fatigue cycles.

Unsteady response to a specific distortion can be modeled using CFD methods to a high degree of fidelity. With a focus on understanding the aeroacoustic interaction the analyses used here considers generic harmonics of the distortion. Harmonic responses are calculated from low to transonic speeds for a range of cases. Major phenomena and driving parameters affecting the forcing strength and pressure amplitudes in the blade passage are identified from the analyses.

It is demonstrated that the forcing strength is strongly affected by the cut-on/cut-off conditions upstream and downstream of the blades. Also, depending on design parameters of the blade, the aeroacoustics of the blade passage is important for the resulting forcing. The analyses used are made in 2D over a wide range of flow conditions as well as geometric variations.

The results of the study provides an increased understanding of the harmonic forcing of blades. A simple model is proposed that can identify condition where increased pressure amplitudes in the blade passage may be expected. The sensitivities to parameters may also give some guidance in how design and operation can be adapted to reduce the aerodynamic forcing.
Improving the Performance of Turbomachinery Equipment by Selecting Optimized Materials With Good Thermal Stability
Authors: Langille Michael , Tzedaki Maria , Lorenzino Pablo , Davo Belen
Published: September 2023

It is reported that 65% of blade failure in turbo machinery is due to mechanical failures of the blades themselves [1]. The applied stress together with the higher temperatures can have a direct impact on the life of the impeller. It is therefore critical to evaluate the mechanical properties of materials and their durability at the relevant operating temperatures [1, 2]. In this study we will demonstrate the potential of different aluminum alloys to extend the life of a system by evaluating their durability over time at common operating temperatures. With appropriate testing that simulates the mechanisms involved at working conditions, one can benchmark the performance of different products. Comparisons between different alloys used as impellers in turboexpanders, turbo-blowers, turbopumps, turbochargers and superchargers are made. The most common products used in these applications is 2618-T8 and this alloy has been compared with the more recent 2027-T8 that is designed to withstand temperatures above 100°C. The applications demonstrated here for turbopumps and turbochargers will analyze the performance of 2618-T8 and be compared to the new 2027-T8.

The microstructural differences between the two alloys are presented and will be related to the mechanical properties studied. Overall, 2027-T8 demonstrates improved performance at 150°C compared to 2618-T851 in all aspects of material performance: tensile properties, thermal stability, fracture toughness, fatigue and creep performance. These properties are all critical for choosing the appropriate alloy for an impeller or rotor in order to allow either improved performance or increased component lifetime due to over-performance of this newly studied alloy, 2027-T8.
ICME Modeling of Erosion in Coated Metal Alloys and SiC-Based Ceramic Matrix Composites (CMC’s)
Authors: Eftekharian Amirhossein , Park Joshua , Morscher Gregory N. , Huang Dade , Miraj Rashid , Abdi Frank
Published: September 2023

Aircraft parts and components operate within harsh environments such as high temperatures, sand and debris attacks, and corrosive conditions. Coating is a typical solution to mitigate harsh environment effects and protect multi-layer (substrate, bond coat, and topcoat) components.

However, coated components can experience cracks and bending during process of coating which affects the ultimate functionality and usability of as-built parts due to the manufacturing defects. On the other hand, erosion, which needs to be addressed during the design phase, can limit performance of hot engine components due to EBC/TBC delamination, spallation, and mass loss of CMC as well as fiber breakage and matrix cavity formation.

A physics-based ICME tool that guides designers and analysts for erosion of coated components is highly desired considering the complexity of problem and more importantly cost of extensive testing programs.

The ICME method is based on virtual manufacturing of coating process integrated to virtual testing of erosion. A physics-based multi-scale model is developed to a) track temperature field during coating process, b) support material modeling of substrate, co-bond, and coating including effects of voids and residual stresses, c) simulate cracks and deformation due to coating, and d) determine erosion rate and cavity size and depth caused by the high velocity impact of erodent particles and high temperatures by considering cracks and anomalies introduced during manufacturing. For this purpose, the ICME tool employs a thermo-physics code for thermal properties and a micro-mechanics solution that degrades mechanical properties based on temperature and voids during coating. The degraded mechanical properties including damages and cracks are then applied to an augmented dynamic finite element analysis that calculates progression of erosion due to bombardment of SPH particles and tracks mass loss, delamination, and damages of material constituents.

The ICME tool is test validated for two cases: 1) SiC ceramic panels coated with EBC and 2) Stainless steel substrate with TBC coating. For both examples, simulation results show agreement with test in terms of mass loss and crater size due to erosion. Simulation also demonstrates that coated components suffer from cracks and damages due to coating which can exacerbate erosion rate. Finally, the ICME method is used to predict erosion of a coated SiC/SiC CMC specimens at high temperatures, where multi-scale progressive failure analysis considers fiber/matrix interphase as well as manufacturing defects due to coating process.
Effect of Fuel Injection Method on Flame Characteristics and Exhaust Gas Emission of CO2-Diluted Methane Oxy-Flames
Authors: Jeon Kitae , Lee Jong Guen
Published: September 2023

The effect of fuel injection method on flame characteristics and exhaust gas emission is investigated for a single micro-mixer combustor, running on CO2-diluted oxy-fuel at 4 and 8 atm. The CO2 fraction in CH4/CO2/O2 mixture is fixed at 70% (by volume). The mean flow velocity in the mixing section is fixed at 25 m/sec and the equivalence ratio is varied from stoichiometric condition to LBO (Lean blow-out limit) condition. In addition to completely premixing case, two different injection methods are employed: VI (vertical jet-in-crossflow injection) and TI (tangential jet-in-crossflow injection) where fuel (CH4) is injected at 0.18 m upstream of combustor inlet in the mixing section. Results shows that the degree of premixing between fuel and CO2/O2 mixture is an important parameter in determining combustion efficiency as well as flame structure for CO2-diluted methane oxy-flame and higher combustor pressure results in higher combustion efficiency with a minimal effect on flame length. The tangential jet-in-cross flow injection results in better premixing than the vertical jet-in-crossflow injection. The vertical jet-in-crossflow injection of fuel results in slightly longer flame than perfectly premixed case and the tangential-entry injection of fuel results in the shortest flame. Better premixing between fuel and CO2/O2 mixture leads to higher CO2 and the lower O2 and CO emission over the range of equivalence ratio, suggesting better premixing leads to more complete combustion and hence higher combustion efficiency. Also, more fraction of CO2 can be added into combustor without causing blowout for better premixing cases such as premixed injection and tangential jet-in-crossflow injection.
Influence of a Rib in the Diffuser of a Low-Pressure Steam Turbine on Aerodynamic Excitation at Part Load Operation
Authors: Doll Philipp , Müller Fabian F. , Schippling Stefan , Vogt Damian M. , Aschenbruck Jens
Published: September 2023

In recent years, the requirement profile for steam turbines used for power generation has changed significantly. In addition to highly efficient, eco-friendly and continuously available electricity generation, further demands have become more and more important: flexible operation in an extended operating range, compensation for short term fluctuations caused by renewable energies, and improved efficiency at part load.

Due to the more flexible operation, steam turbines operate frequently at part load. At such operating conditions, excitation phenomena can occur in the flow field, potentially leading to forced vibrations of the last stage rotor blades. A possible phenomenon in this context are rotating instabilities (RI). RI are vortex structures moving circumferentially at a certain frequency in the axial gap between guide vane and rotor blade triggered by flow separations in the blade path.

In the first part of the paper, excitation phenomena at part load operation are experimentally investigated in a model steam turbine. The outer casing of the turbine is equipped with unsteady pressure sensors at various circumferential positions upstream and downstream of the last stage rotor blades to identify operating conditions at part load where RI occur. The radial location and extent of the RI are determined by means of unsteady pressure probe traverses in the axial gap between guide vane and rotor blade.

In the second part of the paper, the influence of a supporting rib in the close vicinity to the last stage blade row on the location and intensity of the RI is investigated both quantitatively and qualitatively.

The occurrence and appearance of RI at various operating conditions is assessed from test data for both the setup without and with supporting rib. Based on the evaluation of this test data, it is shown that the pressure excitation caused by RI is significantly reduced by the rib.
A Compressor Wheel Design for Noise Reduction Due to Pressure Gradient in an Automotive Turbocharger
Authors: Jung Wonbae , Kim Seongsoo , Noh Taeho
Published: September 2023

In the most industries that manufacture compressors, it is very common to encounter noise issues on the compressor wheel while its operation. This noise is likely due to a pressure gradient along the compressor blades with inlet air flowing through them. This paper presents experimental and numerical investigations of noise reduction for the compressor wheel of an automotive turbocharger by modifying its geometry such as inlet area, inlet and outlet beta angles. The numerical model includes a one-dimensional aerodynamic analysis of the inlet and outlet operating conditions and describes meridional design of the compressor wheel. The design parameters include compressor inlet diameter, trim ratio, throat area, inlet and outlet beta angles, etc. Structural analysis on modal and centrifugal stress verifies the model reliability. CFD analysis of compressor models calculates total and static pressures at inlet and outlet domains, mass flow rate, and aerodynamic efficiency. The experimental data agree well with the numerical predictions while evidences noise reduction from the design method used in this paper. The newly designed compressor wheel meets the desired goals such as maximum efficiency at specific flow rates and rotational speeds and successfully reduces noise due to fluid instability.
Formulation and Validation of a Novel Actuator Line Model for FOWT Applications
Authors: Sanvito Andrea G. , Persico Giacomo , Firpo Agnese , Schito Paolo , Dossena Vincenzo , Zasso Alberto
Published: September 2023

The paper presents a novel in-house CFD solver featuring an original formulation of the Actuator Line Model (ALM), implemented into the OpenFOAM software. The new formulation samples the velocities close to the body-force application point, so to eliminate any effect of the oscillations and disturbance from the sampling. A detailed analysis is conducted using several sampling techniques to achieve proper modelling to be employed in Floating Offshore applications. The proposed formulation is assessed against experiments carried out in the large scale Wind Tunnel of the Politecnico di Milano on a scaled wind turbine laboratory model operated in steady wind and floating conditions. Load cases with both surge and pitching platform motions are considered and simulated with ALM-CFD coupled solver. The new method represents a viable alternative to ALM simulation tools already documented in literature, since it relies on a physical-based spatial velocity sampling of straightforward implementation.
FlameSheet™ Combustion Multi-Platpform Enhancements & Full Interval Validation for Extended Operational Flexibility, Low Emissions & High Hydrogen Capability
Authors: Hernandez Fred , Keshava Bhattu Ramesh , Kalb Bryan , Yaquinto Matt , Vogel Gregory , Rizkalla Hany
Published: September 2023

The quest for greenhouse gas (GHG) reduction is driving the need for higher hydrogen combustion capability for power production, while renewable energies demand more operational flexibility from industrial gas turbines (IGT). The first FlameSheet™ gas turbine combustion system entered commercial operation in 2015 demonstrating high operational flexibility; and in 2022 the fleet leader achieved full interval status of 32k hours of operation demonstrating great durability. Since 2015, there has been significant technology advances on the FlameSheet™ leading to a widening of operational envelope and increased hydrogen capability with lower emissions. This paper provides a detailed inspection of key lifing areas in the combustor after a full 32k hours interval and the validation of the analytical structural analysis predictions. The paper also provides details of FlameSheet™ enhancements of the pilot injector using advanced micro-mixer technology. The latter, combined with the original FlameSheet™ trapped vortex main injector enables improved flammability margin and lower emissions resulting in increased operational flexibility and hydrogen capability to support a renewable penetrated energy market and future provisions of GHG reduction mandates. In addition to the fuel and operational flexibility, provisions to enable multi engine platform compatibility has been implemented, and the paper provides a comparison of the operational characteristics of the FlameSheet™ combustor from a mechanical and aerothermal perspective when operating in an F-Class Siemens Westinghouse 501F, GE 7F.03 or E-Class GE 7E.03 industrial heavy duty gas turbine engine. This paper is a complement to the existing FlameSheet™ paper referenced in [4] which already provided information of the low pressure drop FlameSheet™ combustor variant implementation alongside Power Systems Manufacturing (PSM) Gas Turbine Optimization Package commercial install in an F-Class heavy duty gas turbine.
Applicability of Simplified Data-Driven Models in Gas Turbine Diagnostics
Authors: Loboda Igor , Pérez-Ruiz Juan Luis , González Castillo Iván , Yepifanov Sergiy
Published: September 2023

Gas turbine engine diagnostic algorithms based on gas path measurements constitute the principal subsystem of an engine monitoring system. These algorithms follow two main approaches. The first of them called a Gas Path Analysis (GPA) relies on a physics-based model (thermodynamic model) to transform gas path measurements into engine components’ health parameters. Within the second approach, diagnosis is made in the space of the deviations of measurements from an engine baseline using the pattern recognition theory. This approach mainly employs data-driven models and does not directly use the thermodynamic model. But the thermodynamic model helps to generate the necessary input data.

The thermodynamic model presents a complex software exigent to computer resources. Moreover, the model computation cyclic procedure does not converge sometimes. To simplify diagnostic algorithms and make them reliable, a linear model was introduced in the first GPA studies. Since the linear model is not accurate enough, surrogate nonlinear data-driven models were proposed later.

The present paper deals with the thermodynamic model and three simplified data-driven models for the steady-state operation of an industrial aero-derivative gas turbine. The paper focuses on the influence of the model choice on the final diagnostic reliability. Not only the reliability level is studied with these models, but also the influence of diagnostic conditions is investigated. In this way, the applicability of simplified data-driven models is validated. We hope that the paper results will stimulate the design of simple, but reliable diagnostic solutions and general progress in the development of real monitoring systems.
A Numerical Heat Transfer Investigation of Lattice Structures As an Alternative AM-Enabled Design for Cooled sCO2 Airfoils
Authors: Otto Marcel , Wardell Ryan , O’Neal Parker , Veselý Ladislav , Kapat Jayanta
Published: September 2023

Supercritical Carbon dioxide (sCO2) power cycles are rapidly developing and gaining popularity in waste heat recovery systems, as primary power cycles for a variety of heat sources such as nuclear, or as a stand-alone power cycle where fossil fuels are combusted. Akin to conventional gas turbines, sCO2-powered systems are pushing the boundaries for firing temperatures for higher efficiencies. Direct oxy-fired sCO2 systems will demand internal cooling of the airfoils for safe and reliable operations. Gas turbine cooling technology can be leveraged for that purpose. However, two key differences exist. First, the coolant medium is sCO2 instead of air, and second, sCO2 airfoils are much smaller compared to power-generation gas turbines. Novel AM manufacturing techniques promise advanced internal cooling geometries. This paper investigates a novel trailing edge cooling design to replace conventional pin fin arrays. Here, a lattice structure with microchannels is introduced. The study presents the changes in heat transfer due to the substitution of the heat transfer medium and the new geometry. The component is assumed to be printed Inconel 718. Based on an oxy-fired combustion sCO2 power cycle, coolant temperature and pressure and hot gas path temperature and pressure are chosen. The converging trailing edge duct is simulated in StarCCM+ using COOLPROP for sCO2 properties as a conjugate heat transfer model.
Performance Characteristics of a Rotating Detonation Combustor Exiting Into a Pressurized Pleunum to Simulate Gas Turbine Inlet
Authors: Talukdar Shaon , Langner Dalton , Gupta Apurav , Agrawal Ajay K.
Published: September 2023

The present study aims to experimentally characterize the performance of a rotating detonation combustion (RDC) system integrated with a pressurized downstream plenum to simulate the high-pressure inlet conditions of power generating gas turbines. A thorough understanding of the operational behavior including wave mode behavior, static pressure profile along the combustor length, and dynamic features of pressure fluctuations is crucial for successful integration of RDC with the turbine. In this study, two RDC configurations are investigated, RDC with a constant area annulus and RDC with a converging nozzle. In both cases, the RDC flow exited into a plenum chamber kept at pressures varying from 155 kPa to 330 kPa. RDC was operated on methane and oxygen-enriched air to represent reactants used in land-based power generation. Experiments were conducted for the two RDCs configurations operated at three reactant mass flow rates (0.23, 0.32, 0.46 kg/s). The RDC performance is characterized by time-averaged static pressures measurements, and wave velocity determined by ionization probes. In addition, dynamic pressure measurements were recorded both inside and near the exit of RDC channel to investigate wave interactions between RDC and downstream plenum. Results show that the RDC with the converging nozzle achieved superior performance while minimizing detrimental interactions with the reflected shock and/or acoustic waves from the downstream plenum.
Diagnostic Strategies for Microturbines Operating Status Applied to Predictive Maintenance: Experimental Test Case
Authors: Álvarez Eduardo Á. , Yosry Ahmed G. , Fernández Jiménez Aitor , Calleja Rodríguez Antonio , Rico Secades Manuel
Published: September 2023

The current study represents a preliminary step towards detecting operating problems in wind microturbines automatically. The electrical frequency signal generated by the turbine allows for the detection of operating issues during its power stage. To conduct a comprehensive study, a vertical-axis microturbine has been tested, under various failure conditions, inside a closed-loop wind tunnel. An electronic data acquisition system has been developed to continuously measure the frequency signal during the experiments. The output data, including the power and the frequency signals, has been analyzed in terms of average frequency and standard deviation. The collected and stored data is accessible through an operation and maintenance system, which uses an AI-based algorithm and a Jupyter Notebook tool that is executed in Python.
A Robustness Assessment of a Fiber Optic Particle Sensor for Aerospace Turbomachinery
Authors: Overbaugh Malcolm , Esquivias Brandon , Li Alice , McDonell Vincent , Waldherr Gregor A. , Lin Hai
Published: September 2023

Various regions globally are prone to specific weather events and contain geologic features that promote high concentrations of airborne particles, consequently causing the aircraft operating in these regions to endure reduced safety and inferior performance. The ingestion of airborne particles of unknown type and measure into aerospace turbomachinery can cause unpredictable failures and subsequent reductions of propulsion, indicating the need for more accurate preemptive maintenance schedules for aircraft engines to avert most major failures. The installation of an on-board sensor capable of determining the type and concentration of particles entering the engines of an aircraft would provide the data necessary to adjust maintenance schedules and make operating aircraft in particle laden conditions safer. This study demonstrates the methods used in the design of a proprietary fiber optic particle sensor for non-intrusive real time measurement, which sizes the ingested material and measures its distribution and concentration directly in an engine’s flow path. A test rig was devised to provide high velocity and high temperature, contaminated flow using ISO 12103-1 A3 Medium Test Dust. Durability tests using this system consisted of exposing the sensor probe to prolonged periods of high velocity dust exposure, high temperature flow up to 275 °C and modeled aircraft vibration using MIL STD 810H: Method 514.8 – Vibration, Annex D, Category 22, and Method 516.8 – Shock, High Speed Craft II and Functional Shock – Procedure I. The results from these tests were compared to cold flow test data to determine the operational limits of the sensor and assess the feasibility of incorporating such a sensor into current and future aerospace turbomachinery. The results indicate that the fiber optic sensor probe is robust to dust exposure, temperature, and vibration, and was able to consistently size and count the test dust, thus building confidence towards demonstration in a high-fidelity environment.
Performance Characterization of a Small-Scale Pumped Thermal Energy Storage System
Authors: Smith Natalie R. , Just Joshua , Johnson Jeremy , Karg-Bulnes Fernando
Published: September 2023

Long-duration, grid-scale energy storage technologies provide a potential pathway to enable full penetration of renewables on the electricity grid and still maintain grid reliability and security. Among these technologies, pumped thermal energy storage (PTES), which stores energy thermally using a heat pump and discharges the stored thermal energy with a heat engine when needed, is an advantageous solution with high round trip efficiency, no geographical constraints, and modularity for various use cases. To support the technology development, a first-of-a-kind small scale demonstration facility of an air-based PTES has been designed, built, and tested with the objective of better understanding controls strategies and overall system operation. The PTES demonstration facility operates simple-recuperated cycles for charge and discharge mode with separate drivetrains for each mode and shared heat exchangers and storage systems. At a discharge mode rating of 5kW, this facility storages heat in a thermal oil up to 350 °C and cold in a water-glycol mixture down to −10 °C. In this paper, full system performance characterization is described with steady state and transient data from both charge and discharge modes during start-up, shut down, steady state, and system balance. Time series temperature data comparisons of a cold and warm startups are compared. These data highlight the importance of transient control tuning, the influence of ambient effects, and challenges associate with first implementation of a technology, particularly heat loss. This study documents the first of a kind operation of a full air-based PTES system.
Super-Critical Carbon Dioxide Power Cycle for Waste Heat Recovery Utilizing Hermetic Oil-Free Turbomachinery: Cycle and Conceptual Turbomachinery Design
Authors: Ertas Bugra , Zierer Joseph , McClung Aaron , Torrey Dave , Bidkar Rahul A. , Hofer Doug , Rallabandi Vandana , Singh Rajkeshar , Zhang Xiaohua
Published: September 2023

This paper focuses on the conceptual design of a supercritical carbon dioxide (sCO2) waste heat recovery (WHR) power drivetrain for application to natural gas (NG) compressor stations. The first goal of this work was to determine the potential benefits from operating a sCO2 WHR unit with a novel oil-free hermetically sealed dual-spool power drivetrain. A second objective was to identify existing technology gaps and risks that surfaced through the design process. The drivetrain configuration utilizes process gas lubricated bearings and an immersed electric machine, which enables oil-free and leakage-free operation of the power system. The concept adopts a cascaded Brayton bottoming cycle powered from the 510 °C and 89 kg/s exhaust of a 34MW aeroderivative gas turbine used in NG compression stations. Operating boundaries for the proposed bottoming cycle reside between 237 bar, 485 °C and 85 bar, 133 °C. The proposed concept utilizes a dual spool drivetrain configuration possessing a high-speed gas-generator rotor aerodynamically coupled to a low-speed power turbine. The results from the study showed that the oil-free drivetrain configuration has the potential to increase the aeroderivative gas turbine simple cycle efficiency of 41% to a combined cycle efficiency of 51% with a potential of generating an additional 8.5 MWe of emission-free power from the bottoming cycle. Key risks identified for advancing the concept include bearing load capacity, rotordynamics, and thermal management. Finally, the proposed oil-free hermetic sCO2 power system is compared to an installed Organic Rankine Cycle (ORC) specific case study, which was particularly useful when comparing output power, recovered energy, and improved efficiency of the present concept.
Industrial Wireless Cyber-Physical Systems Performance Using Deep Learning
Authors: Kashef (Hany) Mohamed , Candell Richard , Montgomery Karl
Published: September 2023

Industrial wireless communications networks have a major role in the future industrial cyber-physical systems (CPSs) by allowing higher flexibility and massive machine connectivity. However, the reliability and latency of industrial wireless networks need to be evaluated accurately to ensure satisfying the industrial CPS requirements and analyze degradation factors. In order to measure the impact of deploying industrial wireless on cyber-physical system performance, a deep learning framework based on the generative adversarial network (GAN) is introduced. The GAN is used to model the performance of the system and identify the impact of various wireless impairments on the system performance. The GAN model can deploy features from both the wireless network and operational performance spaces. The loss function of the discriminator part of the GAN is deployed as a performance metric that can be used to model the average performance of a specific wireless scenario and compare to the normal behavior of the industrial wireless system. The proposed GAN-based methodology is validated using a dual-robot collaborative lift use case in which IEEE 802.11ac is employed.
Multi-Axis 3D Printer Design Challenges for In-Situ Additive Manufacturing
Authors: Rudd Liam , Campbell Matthew I. , Alonayni Ghazi
Published: September 2023

Multi-axis Additive Manufacturing (AM) is a prevalent technology that is currently limited to machines that only operate within enclosed volumes. Such an enclosed volume limits the size of additively manufactured parts. However, if the printing happens outside of the printer, the print-volume is unbounded. Furthermore, in adjacent printing, one could create and join a part at its eventual assembly — thus removing a step in the manufacturing process. A mobile machine like this would allow the operator to print infinitely sized parts on any surface and printing parts directly onto the work surface removes the post-print assembly costs and times. Robotic manipulators are commonly used in research applications of adjacent multi-axis 3D printing due to the accessibility and kinematic freedom of these machines. But, while robotic manipulators can print in many different orientations and on a variety of surfaces, the lack of rigidity in the rotational joints and complex inverse kinematics associated with them means that printing with these machines can be overly complex and yield imprecise results. This paper examines both the hardware and software design challenges in creating a novel multi-axis 3D printer designed specifically to print onto arbitrary surfaces directly adjacent to itself. Kinematics and joint rigidity are carefully examined in order to design an optimal configuration. Given the chosen kinematics, the computational systems needed to control the printer are presented in detail including calibration, part slicing, and toolpath creation.
Review of Recent Methods and Learning Techniques in Prediction of Tool Life
Authors: Izdihar Ulfa Fairuz , Patel Brijesh , Huang Zih Fong , Yeh Chih-Ho , Lin Po Ting
Published: September 2023

The reliability of the cutting tool is a key factor in accomplishing the objective of the machining processes. The methods and learning techniques to predict the tool life have been studied for several decades on basic machine tools, including milling, turning, and also drilling as a part of a smart manufacturing system. The current state of the cutting tool is used for modeling the tool’s life. The undesired condition throughout machining, such as excessive vibration, will affect the tool life directly due to the tool failure, including chatter, wear, and breakage. The prediction of tool life using Tool Condition Monitoring Systems (TCMS) is fundamental for manufacturing productivity and also cost-effectiveness. It is implemented by using advanced sensors for data acquisition and determining the process parameters as well as vibration, sound, and cutting force are collected, either directly or indirectly. Signal processing methods and Artificial Intelligent (AI) classifiers are used to obtain the current state of cutting tools during machining processes. This paper reviews various methods and learning techniques of TCMS in predicting the tool life for different machining processes. An experimental tool life prediction was performed by using K-mer signal recognition as feature extraction for sound signal data collected by the microphone for the CNC turning process on alloy steel. Then, Support Vector Machine (SVM) is used to show the accuracy of the method. The experimental results have shown that it is feasible to apply K-mer signal recognition as feature extraction and SVM as machine learning to predict the tool life with 95% accuracy.
Semi-Automated Soft Robotic Stamp Transfer Machine for Van Der Waals Heterostructure Device Assembly
Authors: Ahn Seong-Hyo , Chavarria Juan , Mu Haoxuan , Liao Yifeng , Warner Jamie , Zhou Lei
Published: September 2023

Monolayer materials can be vertically stacked into artificial solids, known as the van der Waals heterostructures (vd-WHs) [1], to realize a new class of ultrathin optoelectronic, electronic, and quantum devices, which have significant potential to revolutionize the field of nanoelectronics and impact a wide range of application areas including transparent displays, sensor arrays, and logic and memory circuits. However, today’s assembly of vdWH devices is still primarily through manual manipulation, which lacks the precision and repeatability needed for the scalable manufacturing of wafer-scale vdWH device arrays outside a research setting. Aiming to enable the automated, scalable, and repeatable manufacturing of vdWH device arrays, this paper presents the design, prototyping, and preliminary tests of a novel semi-automated soft-robotic stamp transfer system for thin-film materials. The system uses a dry elastomer stamp with its adhesion controlled by temperature and peeling speed for material transfer. A combination of electromagnetic and pneumatic actuation is used for the soft-robotic stamp to realize a gentle and uniform pressing of the stamp over the material. An optical microscope, force sensors, and temperature sensors are integrated to enable instrumentation of the transfer process. Preliminary experiments were conducted using our system to conduct for exfoliated graphite transfer. Test results demonstrate the reliable and repeatable transfer of 2D crystal flakes, which show promise to enable the deterministic and scalable assembly of vdWH-based device arrays at wafer scale.