bluuebunny/crossref_metadata_2025 huggingface dataset:
Unsteady Pressures During Frequency Lock-in of a Cylinder Experiencing Non-Synchronous Vibrations
Authors: Hollenbach Richard , Sanz Isabelle , Kielb Robert
Published: September 2023

When an unsteady aerodynamic instability coalesces with a natural mode of vibration, Non-Synchronous Vibrations (NSV) can occur. Often in turbomachinery, vortex shedding, or tip gap flow causes frequency lock-in to the compressor or turbine blade bending or torsional natural mode of vibration. This can cause limit cycle oscillation (LCO) and ultimately blade failure. There is no current design tool for NSV that engine manufacturers can use; rather, expensive wind tunnel testing and time-consuming 3D computational fluid dynamics (CFD) are conducted to search for it. While studies have been done on turbomachinery geometry to study NSV, simpler configurations need to be studied first to understand the underlying flow physics. In this work, a cylinder undergoes enforced oscillations transverse to oncoming flow in the von Karman Vortex Street flow regime. The unsteady pressures are studied in both unlocked and lock-in conditions. In this context, this paper attempts to model the unsteady pressures of the lock-in region as a linear combination of unlocked amplitudes. Once the frequency content is collected for multiple cases, the unlocked data is fed into a Multiple Linear Regression to predict the lock-in data, with very good agreement. Previously shown was the coefficient of lift linearly increases with increasing amplitude of oscillation while locked in. The first study validates this finding. However, when unlocked first, the pressure contributions from various frequency ratios linearly combine to recreate the pressure loading for the lock-in cases. Finally, pressure amplitudes for various unlocked amplitude ratios linearly combine to form the same lock-in pressure loading. Unsteady pressures are not measured and do not often appear in literature. In addition, the unsteady pressure contributions have not previously been split up between the enforced motion and the vortex shedding, making this work novel.
Concentrated Solar Power Coupled With Waste Heat Recovery System for Innovative Clinker Calcination Process
Authors: Vesely Ladislav , McLaughlin Luke , Álvarez Francisco , Kapat Jayanta
Published: September 2023

The decarbonization of energy-intensive industries (i.e., cement) is a key challenge to reduce CO2 emissions worldwide and achieve zero-emission production. CO2 emission can happen through three different pathways in a cement plant: directly through (1) use of CO2-emitting heat sources, and (2) emission of CO2 generated in the calcination process, and indirectly through (3) use of electricity from the grid that is not fully green. The decarbonization of the cement process can be carried out by two different approaches (i.e., direct - alternative fuel or energy source and carbon capture systems, indirect - utilization of waste heat). This paper is focused on a novel cement process system that addresses pathways necessary to reduce the CO2-footprint of cement production. The proposed system consists of concentrated solar power (CSP), thermal energy storage (TES), and waste heat recovery systems (WHR). The exhaust stream can be connected with carbon capture and sequestration system (CCS). This allows the cement process to continue in production without downtime. The presented work is a concept study of the proposed system is based on current state of the art of individual subsystems. A complete analysis and optimization are performed for the sCO2 WHR power cycle as well as CSP and TES. The results show potential benefits and disadvantages of the proposed system.
Expansion of Neuber Rule to 3-D Stress States for Anisotropic Materials
Authors: O’Nora Nathan , Day William D.
Published: September 2023

It is often necessary to use finite element analysis (FEA) to understand the stresses experienced by a component when evaluating gas turbine component life. It is necessary to understand the elastic-plastic behavior of the materials for these components, but it may be impractical or cost prohibitive to simulate the inelastic behavior-plastic in FEA due to the much larger computation time. Neuber rule was developed to allow for correlating elastic results to elastic-plastic cases, however, doing so relies upon the use of an effective stress and effective strain calculation in order to be applied. While this works well in isotropic materials, for many anisotropic materials this is poorly suited due to the differences in anisotropy between the failure surfaces, yield surfaces, and plastic flow.

This paper demonstrates the expansion of the Neuber rule expanded to 3-D stress states and 3-D anisotropic material models by applying the rule for each component of the stress-strain relationship. A hydrostatic stress requirement is also used to ensure the resulting elastic-plastic stress-strain behavior is representative of the elastic case used to generate the stress-state. The method is applied to loadings of conventionally cast (CC), directionally-solidified (DS), and single crystal (SX) materials for both simple and complex loadings, utilizing an anisotropic visco-plastic model for the elastic-plastic behavior. Uniaxial results and complex isotropic loadings are compared to the 1-D Neuber rule to ensure that the 3-D expansion simplifies to the 1-D case where expected.
Design of an Environmental Barrier Coating Bond Strength Test Coupon
Authors: Salem Jonathan A. , Mital Subodh K. , Harder Bryan J. , Thompson Aaron C.
Published: September 2023

The bond strength of an environmental barrier coating (EBC) to a substrate such as a silicon carbide fiber/silicon carbide matrix (SiC/SiC) ceramic matrix composite (CMC) is a function of coating application parameters, matrix surface roughness and environmental exposure, which results in the formation of a thermally grown oxide layer (TGO) layer. Current estimates of the EBC bond strength to a substrate are made assuming that the applied force divided by pull tab area is a representative metric. Although this is an expedient method for rapid strength estimates, the process of bonding the EBC to a pull-tab creates thermo-elastic residual stresses that are superimposed with the applied tensile load. Minimization of these stresses via test specimen design should give the most realistic estimate of EBC bond strength. We examine the residual stresses imposed on the EBC by cooling of an adhesive layer bonded to various metal and ceramic tabs. The results are extended to examine the stress distribution in a thermally grown oxide (TGO) layer formed on a Plasma Spray-Physical Vapor Deposited (PS-PVD) Yb2Si2O7 (ytterbium disilicate) EBC. An EBC/substrate coupon that overhangs a titanium or Kovar® pull tab is recommended in order to minimize thermal stresses, avoid edge effects, and provide an acreage strength measurement. The test method is sensitive to changes in substrate surface finish and oxidation time.
On the Performance of Hydrostatic Journal Bearings in Air, Water, and Liquid Nitrogen: Measurements and Predictions
Authors: Jung Hyunsung , Kim Kyuman , Ryu Keun
Published: September 2023

Turbopumps in reusable and low-cost liquid rocket engines require compact and simple hydrostatic (i.e., externally pressurized) bearings to support large static and dynamic loads at high shaft speeds with no bearing DN life limitation. Hydrostatic bearings are one of the key mechanical components for cryogenic turbopumps to improve their reliability and reusability. Hydrostatic bearings offer significantly enhanced durability with very low friction and wear while providing accurate rotor positioning as well as large load and static stiffness characteristics even working with low-viscosity liquids. The current work measures static load characteristics of hydrostatic journal bearings in air (25°C), water (from 25°C to 70°C), and liquid nitrogen (−197°C). Air, water, and liquid nitrogen are used as test fluids for the test bearing to evaluate the effects of fluid properties and temperatures on the bearing performance. A complete set of applied static load, bearing eccentricity, and bearing supply pressure for each test fluid (i.e., air, water, and liquid nitrogen) is presented for the test hydrostatic bearing. Measurements show that the applied static load on the test bearing significantly affects the recorded journal eccentricity ratio, bearing flow rate, and bearing static stiffnesses. Predictions are in good agreement with measurements. The predictable performance of hydrostatic journal bearings in air, water, and liquid nitrogen can further their application in various cryogenic turbopumps for liquid rocket engines.
Sensitivity Analysis of Transient Forced Response of Mistuned Bladed Disks Under Complex Excitation and Varying Rotation Speed
Authors: Tong Jing , Zang Chaoping , Petrov Evgeny
Published: September 2023

During accelerations and decelerations of gas-turbine engines, the transient vibration effects in bladed disk vibration become significant and the transient response needs to be efficiently and accurately assessed.

In this paper, an effective method is developed for efficient calculations of the sensitivity of the transient vibration response for a mistuned bladed disk under varying rotation speeds. The sensitivities are calculated concerning two major factors: (i) the blade mistuning and (ii) the rotor acceleration/deceleration rates. The method uses the large-scale finite element modelling of the bladed disk to accurately describe the dynamic properties of the mistuned bladed disk. The method can be applied for a case when the loading is the transient load, with the amplitude and frequency spectrum changing with rotation speed. The dependency of the modal characteristics on the rotation speed is included in the formulation of the sensitivity analysis method. Efficient reduced order models are used to reduce the computational cost, which can adapt to the effects of the varying rotation speed on the natural frequencies and mode shapes of the mistuned bladed disk under transient conditions. The expressions for the sensitivities are derived analytically which provides high accuracy and speed of the calculations.

The method has been implemented in a computer code and thoroughly verified using a set of test cases. The studies of transient forced response sensitivity have been performed for realistic bladed disk models.
Temperature Measurement of Model Gas Turbine Combustor Using a Multi-Wavelength Pyrometry in Visible and Near Infrared Spectrum
Authors: Haidar Rifat , Lee Jong Guen
Published: September 2023

Continuous control and monitoring of the gas turbine combustor wall is essential for preventing combustor liner from overheating which may significantly damage structural integrity and reduce overall lifespan. In the past half century combustor outlet temperature has risen from 1100 to 1850 K. The continuous increase of severity of operating conditions inside combustor demands for a temperature determination method whose operation and accuracy are not affected by ever rising temperature. Conventional methods such as thermocouples and thermographic phosphor are not only intrusive, but their operation is also either restricted by an upper temperature limit (thermocouple) or measurement accuracy significantly decreases with increasing temperature beyond a certain threshold (thermographic phosphor). In this paper a multi-wavelength pyrometry system is developed which provides a fast, minimally intrusive temperature determination of the combustor wall. This method does not require any prior knowledge of exact emissivity but of the functional relationship between emissivity and wavelength over the spectral region of interest. One of major problems of wall temperature measurement using a pyrometry in combustor is that the emission from the combustor wall is interfered by the emissions from molecular radicals existing in the flame such as CH* (∼431nm), OH* (∼308nm), CO2* (400–600 nm) in the visible range and major species such as H2O (1.4,1.9,2.7,6.3 um) and CO2 (2.7,4.3,15 um) in the infrared region. In this report, a combustor which is made of stainless steel and runs on natural gas is used and the spectrum of flame emission is measured to identify a proper wavelength range (650–800 nm) over which there exists minimal or no interference from flame emission with thermal radiation. Thermal radiation is measured within the mentioned spectral range with spectrometer and camera assembly from the target spot on the combustor wall with temperature ranging from 1000 to 1200K. Measured temperatures are found to be in good agreement with temperatures measured with thermocouple with absolute error being within 5% or less.
Effect of a Passive Flow Control Device on the Performance of an S-Duct Inlet in High Subsonic Flow
Authors: Rider Courtney , Asghar Asad , Allan William D. E. , Ingram Grant , Stowe Robert , Pimentel Rogerio
Published: September 2023

Embedded engines requiring S-duct diffusers as inlets have long experienced flow separation and distortion. This paper presents an investigation of passive flow control with the application on S-duct diffusers. The flow control is in the form of stream-wise tubercles aiming to improve performance through increasing boundary layer momentum and keeping flow attached in previous regions of separation. Tubercles have shown to increase post-stall performance for airfoils and are similarly applied to the suction surface when used in internal aerodynamics. This paper compares results from experimental testing and computational fluid dynamics (CFD) simulations. The experimental results measured surface pressure with static surface ports, and at the exit, total and static pressure measurements were recorded with a 5-hole AeroProbe. The implementation of flow control led to decreased or mitigated separation regions developing into a more uniform pressure at the aerodynamic interface plane. Similar results were evident in the CFD simulation. A k-ω SST model was chosen since it has shown to better predict the separation regions. A high y+ model was used since additional improvement in separation modeling. The same trends were seen in simulated pressure recovery and in swirl when comparing the use of flow control to the baseline duct performance.
Part Load Combustion Testing of a Low NOx Combustor With Hydrogen-Methane Fuel Mixtures
Authors: Beck Griffin , Cunningham Seth
Published: September 2023

Currently, electricity markets are beginning to experience substantial increases in renewable energy generation. Some of these renewable energy sources have a highly variable output in an uncontrolled manner. In order to maintain grid stability, there is a need for power plants to ramp up power supplied to the grid rapidly to make up for drops in renewable generation. This is often termed spinning reserve, but the size of this reserve may need to increase as renewable penetration into the electricity market increases. Small combined heat and power (CHP) plants provide a promising option for meeting this spinning reserve requirement.

In order to operate in spinning reserve while still meeting the heat requirements for the CHP, the gas turbine needs to operate efficiently at very low loads. Efficient, high turndown operations in engines is often limited by the lean flammability limit of the premixed combustion system. This paper discusses experiments carried out to access the benefits on high turndown performance of adding up to 30% hydrogen into the existing engine combustion system. This will help enhance the lean operability range of the gas turbine combustor. Understanding the limits will have a positive two-fold effect. First, the overall efficiency of the gas turbine at part-load conditions will be increased due to the reduced reliance on variable guide vanes (VGV) to maintain a flammable fuel-air ratio. In addition, expanding the lean operating envelope will allow extension of low emissions operation to lower load conditions, which will increase the ability of the gas turbine, operating in a combined heat and power (CHP) application, to efficiently provide power grid support.
Effect of Strip-Fin Height on Jet Impingement Heat Transfer in a Rectangular Channel With Two Jet-to-Target Surface Spacings
Authors: Alzahrani Yasser S. , Wright Lesley M. , Han Je-Chin
Published: September 2023

An experimental investigation of heat transfer performance in a rectangular impingement channel featuring staggered strip-fins was completed. Four configurations were considered to study the effects of varying the strip-fin height (H/d = 1.5 and 2.75) at two jet-to-target surface spacings (z/d = 3 and 6) on the heat transfer, pressure loss, and crossflow magnitude for an impingement channel with in-line, 4 × 12 impinging jets. Also, the effect of the reference temperature choice, either jet inlet temperature or local bulk temperature, for calculating the local heat transfer coefficients was considered. The regionally averaged heat transfer coefficients were measured at seven Reynolds numbers, based on the jet diameter, (10k-70k) utilizing the copper plate experimental method. The results show that the trend of the local Nusselt number distribution varies along the streamwise direction due to the crossflow effect. The crossflow is similar for all Reynolds numbers at a given jet-to-target surface spacing. The discharge coefficients start to decrease below 0.9 after Re = 50k. Finally, empirical correlations were expressed for the area averaged Nusselt number estimation of impingement channels with pin-fin or strip-fin roughness elements.
Mechanisms Leading to Stabilization and Incomplete Combustion in Lean CH4/H2 Swirling Wall-Impinging Flames
Authors: Fan Luming , Savard Bruno , Fond Benoît , Durocher Antoine , Bergthorson Jeffrey , Carlyle Spencer , Vena Patrizio
Published: September 2023

In gas turbines, confined highly turbulent flames unavoidably propagate in the vicinity of a relatively cool combustor liner, affecting both the local flame structure and global operation of the combustion system. In our recent work, we demonstrated, using simultaneous [OH] × [CH2O] PLIF and stereo-PIV, that lean CH4/H2 flames at a high Karlovitz number can present a highly broken structure near wall, highlighted by a diffuse CH2O cloud which suggests local quenching and incomplete oxidation. Such high Karlovitz numbers were achieved using an inclined plate, which substantially extended the lean flammability of the low swirl flames. Yet, how a cooled wall acting as a heat sink played a conducive role in stabilizing high Ka flames remains unanswered. In addition, the origin of the CH2O cloud is also unclear. Hence, in this work, we look to better understand the stabilization mechanisms for lean and ultra-lean flames on the same configuration, and how they may change with a parametric variation of plate incident angle, plate-nozzle distance, and bulk velocity up to the critical values that lead to flame blow off. The results show that the impinging swirling flow creates a low speed region that helps hold the flame, while the wall prevents mixing with ambient cold air. The production of diffuse CH2O, which indicates the occurrence of local quenching, is associated with a mean strain rate K beyond the extinction strain rate Ke. For CH4 flames, most of the reaction zones reside within |K|/Ke < 1; for 70% H2 flames at ϕ = 0.4, the reaction zones are highly broken and scattered in a large area where |K|/Ke < 8, the interspace of which is fully filled by CH2O. In other words, high H2 fraction flames appear to be more robust to persistent strain rate, thus extending their stability envelope. However, these flames can subsist as highly broken flames featuring strong incomplete combustion.
Role of the Equivalence Ratio on Soot Formation in a Perfectly Premixed Turbulent Swirled Flame: A Combined Experimental and LES Study
Authors: Maffina Aurora , Roussillo Mathieu , Scouflaire Philippe , Darabiha Nasser , Veynante Denis , Candel Sebastien , Franzelli Benedetta
Published: September 2023

The understanding of processes that govern soot production in aero-engines is fundamental for the design of new combustion systems with low environmental impact. For this, the development of numerical models that allow for soot accurate prediction for a limited computational cost is required. Many combustors, more specifically those used in aero-engines, feature rich flame regions typically exploited in the so-called Rich-Quench-Lean (RQL) technology. Thus, it is important to complete the data on soot formation in turbulent flames that exist in the literature, by considering rich turbulent flames operating in the premixed mode. To this purpose, a model scale swirled combustor, called EM2Soot, was designed at the EM2C laboratory to analyze soot production under perfectly premixed rich conditions. In this work, the effect of the equivalence ratio on soot production in this burner is experimentally characterized and numerically simulated. Measurements of Planar Laser Induced Fluorescence of Polycyclic Aromatic Hydrocarbons (PLIF-PAH) were performed to examine soot precursors presence, whereas soot volume fraction is measured with Planar Laser Induced Incandescence (LII). Large Eddy Simulations (LES) are carried out using an analytically-reduced chemistry for the gas phase simulation in combination with a three-equation model for the solid phase description. By considering a range of equivalence ratios, the soot volume fraction from the experiments was found to reach a maximum near ϕ = 1.8, whereas a lower level of soot volume fraction was measured for lower and for higher equivalence ratios. The large eddy simulations performed in parallel are found to be in qualitative agreement with experimental data in terms of PAHs location and soot presence. The soot volume fractions fv are notably overestimated with respect to the LII measurements, suggesting the need for improved modeling schemes. However, the numerical results correctly retrieve a reduction of soot production for the highest considered equivalence ratio value and can be used to explain the experimental behaviour. Results indicate that LES gives access to a qualitative understanding of the interactions between flame, turbulent flow, and precursors governing soot formation in this system.
Application of Closed-Loop Output Error System Identification to an SOFC Gas Turbine Hybrid Using a Cyber-Physical Approach
Authors: Amoafo Mychal , Zhou Nana , Bonilla-Alvarado Harry , Tucker David
Published: September 2023

Dispatchable hybrid integrated energy systems provide opportunities for meeting the flexibility essential to the transition of the power sector to net-zero carbon. Integrated energy systems have shown promise in meeting the dispatch challenges resulting from the increasing penetration of intermittent renewable power generation in the energy grid. While these integrated cycles offer high part-load efficiency and high slew rates, the coupling of such disparate technologies creates integration issues and multiple control states. To extend the application of more simplified controllers, like PID, in hybrid power systems, adaptive control will be necessary. Implementation of classic system identification at multiple states in equipment with developing technologies represents significant risk.

A Closed-Loop Output Error (CLOE) system identification method was applied to a hardware test facility at the National Energy Technology Laboratory. The CLOE system identification method was used to develop open loop transfer functions from a closed-loop process using the controller gains. Experiments were carried out using the hardware of the integrated energy system to test and validate the CLOE methodology. The coefficients of each CLOE transfer function were compared to open loop transfer function from formal system identification performed at 100% and 50% load respectively to determine the value of the method in reducing risk associated with controller development in hybrid power systems.
The Impact of Oxidation-Induced Degradation on Materials Used in Hydrogen-Fired Microturbines
Authors: Romedenne Marie , Pillai Rishi , Dryepondt Sebastien , Pint Bruce
Published: September 2023

Hydrogen-fueled microturbines are being considered as part of the future green microgrid. However, the use of hydrogen as a fuel presents new challenges for selection and development of suitable high temperature materials for hydrogen combustion. The burning of hydrogen is expected to result in higher operating temperatures and higher than typically observed water vapor contents in exhaust gases versus burning natural gas. In the present work, foil specimens of various Fe- and Ni-based alloys were oxidized in air + 10 % H2O and air + 60% H2O for up to 5,000 h at 700 °C to simulate the exhaust atmosphere of natural gas and hydrogen-fueled microturbines. The impact of alloy composition and water vapor content on the oxidation/ volatilization induced loss of wall thickness was experimentally evaluated. Enhanced external oxidation and volatilization of Cr2O3 and Ti-doped Cr2O3 scales was observed in air + 60% H2O compared to air + 10% H2O. No significant impact of the higher water vapor content was observed on Al2O3 scales formed on Fe-based alumina forming alloys. Lifetime modeling was employed to predict the combined effects of water vapor content, gas flow rates, temperature and alloy composition on the oxidation-induced lifetime of the investigated materials.
Unsteady Investigation of Intermediate Turbine Ducts Under the Influence of Purge Flows
Authors: Merli Filippo , Krajnc Nicolas , Hafizovic Asim , Schien Malte , Göttlich Emil
Published: September 2023

The aerodynamic flow field at the outlet of a high-pressure turbine (HPT) stage in a modern turbofan engine is highly unsteady and strongly influenced by periodic fluctuations from the HPT rotor, also interacting with the HPT stationary vanes. Downstream of the last HPT stage, the flow enters the intermediate turbine duct (ITD), where new unsteady components are generated, due to the interaction between the incoming flow and the struts supporting the ITD.

This paper illustrates the differences between the unsteady flow behavior in two state-of-the-art ITD configurations for turbofan engines: the turbine center frame (TCF), with symmetric strut fairings (typically adopted in conventional dual-spool engines), and the turbine vane frame (TVF), which is commonly used in geared turbofan engines and incorporates the first low-pressure turbine (LPT) vane row inside the duct.

The experimental results discussed in this work are conducted in the Transonic Test Turbine Facility, situated at Graz University of Technology. To achieve engine-representative operating conditions at the ITD inlet and outlet sections, the tested setups include not only the ducts (TCF or TVF), but also the last HPT stage and the first LPT stage row. Additionally, the test rig features a secondary air supply system, capable of feeding purge air to every stator-rotor cavity in the test vehicle, with independent mass flow and temperature control.

Unsteady measurement data at the inlet and outlet of the two duct configurations are acquired with fast-response aerodynamic pressure probes, for two purge flow conditions. Azimuthal mode decomposition is applied to phase-averaged data at selected radial positions, to isolate and quantify the contribution of different interaction modes to the overall unsteady flow field.
Experimental Investigation on Overall Effectiveness of Flat Plate Combined Impingement Cooling With Film-Cooling of Diffusion Slot Holes
Authors: An Bai-Tao , Hu Jia-Jun , Liu Jian-Jun
Published: September 2023

An experimental investigation on the overall effectiveness of combined film-impingement cooling was performed on single-row and double-row flat plate models. The experiments were carried out in a low-speed wind tunnel using a temperature-sensitive paint (TSP) measurement technique. The temperature difference between the mainstream and the cooling air was approximately 40°C, which corresponds to a coolant-to-mainstream density ratio of 1.13. The mainstream Reynolds number based on flat plate width was approximately 2.8 × 105. Three film hole geometries, including typical fan-shaped hole and diffusion slot holes with cross-sectional aspect ratios of 3.4 and 4.9, were combined with impingement cooling with an impingement hole number to film hole number ratio of 3.2. Five blowing ratios from 0.5 to 2.5 were tested and compared. The Biot number on the mainstream side was in the range of approximately 1.7 to 3.4, depending on the cooling performance. It is shown that under high Biot number conditions, the contribution level of impingement cooling to the overall effectiveness is far less than that of film cooling. Although the trend is consistent, the overall effectiveness difference caused by various hole geometries is lower than that of the adiabatic film cooling effectiveness in magnitude. Regardless of the single-row or double-row configuration, the overall effectiveness of the configurations with diffusion slot holes is always significantly higher than that with fan-shaped holes, in which the diffusion slot hole with a larger AS behaves better.
Implementation of Similarity Principle and Scaling Laws for Low-to-High Speed Mixed Flow Compressor
Authors: Kumar Hemant , Mistry Chetan S.
Published: September 2023

In this paper, the use of the similarity principle has been presented to extrapolate the performance and results for mixed flow compressors application in a small jet or turbofan engines. The similarity principle helps in scaling a single-stage mixed flow compressor model tested at variable operating conditions to different multistage compressors operating to varying conditions through scaling the non-dimensional compressor characteristics. To implement the similarity principle, performance governing parameters were selected and scaling laws were derived, which gives us a degree of freedom for extrapolation of mixed flow compressors. The compressor has been scaled to new specifications using the (ns–π) specific speed-total pressure ratio plot, along the best-efficiency line of the baseline compressor. In this paper, a distinctive approach is taken for validating the scaling laws; the input and output for the scaling laws are target performance (ns–π values) and scaling factors, respectively. The practical use of the scaling laws has been demonstrated by scaling a high-speed mixed flow compressor (maximum total pressure ratio, πmax = 4.55) to new required specifications (π max = 1.03), and examining the conditions under which these laws are applicable. The formulated approach developed for extrapolation of the results from low-to-high speed mixed flow compressors has been justified and tested by comparing the computational results. The impact of dimensions those are not considered (tip gap and splitter blades) for scaling law formulations on flow field distribution is computationally analyzed.
Numerical Investigation of Windage Loss and Heat Transfer in a High-Speed Flywheel Energy Storage System With Slit Wall
Authors: Eltaweel Mahmoud , Herfatmanesh Mohammad Reza
Published: September 2023

Energy storage has recently emerged as a topic of discussion in the context of the energy transition away from fossil fuels. The flywheel energy storage system (FESS) is gaining popularity due to its distinct advantages, which include long life cycles, high power density, and low environmental impact. However, windage loss significantly contributes to total losses in high-speed rotating machines such as the flywheel. Windage loss increases self-discharge, rendering FESS unsuitable for long-term energy storage applications. In the FESS application, the enhancement of heat transfer by the medium within the annulus is crucial. The FESS with a slit wall in the outer cylinder is examined in this investigation to assess the flow field distribution, windage losses, and heat transfer characteristics. The effect of four slit wall geometrical configurations, triangular, trapezoidal, rectangular, and half circle, are investigated in this study. The computational fluid dynamics (CFD) technique is used to model the flow in the annulus of a solid FESS. The results show that the slit wall geometry significantly impacts the distribution of the flow field, the heat transfer process, and windage loss. The fluid is mixed more quickly between the hot and cold sides due to the geometry of the slit wall, resulting in a more homogeneous temperature. As a result, the slit geometry with triangular and rectangular slit walls resulted in the best overall system performance through windage loss reduction and enhanced heat transfer. The findings of this study can assist with the design and optimisation of other rotating machinery with similar flow characteristics.
Partially Cracked Ammonia for Micro-Gas Turbine Application
Authors: Bellotti Daria , Anfosso Chiara , Magistri Loredana , Massardo Aristide Fausto
Published: September 2023

During the last decades, CO2 emissions have increased by 42% with respect to the pre-industrial era. The anthropogenic CO2 is the main source of GreenHouse Gas (GHGs) emissions, contributing, alone, to nearly 30% of global warming effects. The reduction in GHGs emissions to contain the increase in global temperature below 2°C, represents one of the greatest challenges of the XXI century, to ensure the survival of the planet and future generations.

In this energy context, Power to X to Power (P2X2P) solutions are gaining more and more importance in the market considering that, in recent years, the market scenario is increasingly driven by Renewable Energy Sources (RESs). The possibility of storing the exceeding electrical energy production, mainly due to RESs, into hydrogen (H2) or ammonia (NH3) and then turning it back into electricity when RESs power production falls below demand, can improve grid resilience and stability, ensuring, in the meanwhile, a lower environmental impact. Even more, P2X2P represents an innovative solution to increase the flexibility of Gas Turbine (GT) plants, extending their operative range by using alternative carbon-free fuel. Attaining this goal would make GT plants more suitable to trade on the ancillary services market guaranteeing a more secure and clean power system. This study focuses on the use of partially cracked NH3 in micro-Gas Turbine (mGT) applications. To carry out the analysis, a MATLAB/Simulink model has been developed, including also the NH3 storage and the ammonia cracking reactor to simulate an Ammonia To Power (A2P) system. The main thermodynamic parameters, system features, and critical aspects have been evaluated (e.g. the global efficiency, the turbine inlet and outlet temperatures, the power output, etc.) and a comparison between the same system fueled by natural gas and hydrogen has been carried out from the technical and environmental point of view.
Experimental Investigation of Capillary Performance of Additively-Manufactured Lattice Structures for Fluid Wicking Applications
Authors: Kabir Mehdi , Walker Ryan , Eden Chance , Gebre Fisseha , Xu Jiajun
Published: September 2023

In the present study, cylindrical lattice structures of 20 × 40 mm2 (i.e., sample diameter and height, respectively) were fabricated from Maraging Steel (EOS MS1) using the Direct Metal Laser Sintering (DMLS) technique. The lattice structures were designed and fabricated for three different cell topologies, including body-centered cubic, face-centered cubic, and octet truss, with pore opening sizes ranging from 200μm to 1600μm. The present study also experimentally investigates and compares the capillary performance of the printed wick structures, accompanied with characterizing the key porous parameters such as pore size, porosity, permeability, and lattice structures at microscopic scales. Capillary experiments were executed by a rate-of-rise technique to present capillary elevations versus time using methanol as the candidate working fluid of choice with desired merit number to be employed for passive two-phase heat transfer devices for thermal management systems in space applications. Due to the difficulty in locating the meniscus front in lattice structures leading to unreliable data, this work not only takes advantage of an infrared (IR) camera to properly distinguish the front location but also measures the changes in liquid mass wicked into the lattice samples over time, which is another adaptation to the classical capillary rate-of-rise tests.
3D-Fabrication of Hydroxyapatite-Polysaccharide Composite Scaffolds for Bone Tissue Engineering
Authors: O’Malley Ethan , Salary Roozbeh (Ross)
Published: September 2023

The overarching goal of this research work is to synthesize and fabricate mechanically robust, dimensionally accurate, and porous bone tissue scaffolds for the clinical treatment of bone fractures, defects, and diseases. In pursuit of this goal, the objective of the work is to investigate the influence of hydroxyapatite (HA) as well as polysaccharide concentration on the mechanical properties of bone scaffolds, fabricated using pneumatic micro-extrusion (PME) additive manufacturing process. PME has emerged as a high-resolution method for the fabrication of a broad range of biological tissues. This research work tests the following central hypothesis: hydroxyapatite and polysaccharide significantly affect the mechanical properties of PME-fabricated bone scaffolds. A review of literature shows that while hydroxyapatite-polysaccharide composite scaffolds are biocompatible (allowing for mimicking the structure and the function of natural bone), identification of key material and fabrication factors as well as underlying failure mechanisms would be inevitable to achieve mechanically robust, porous bone scaffolds. In this study, based on designed experiments, the HA concentration as well as the polysaccharide concentration (amylose content) were changed in the range of 10–40 % and 7.5–15 %, respectively. Porous bone scaffolds were PME-fabricated using a micro-capillary nozzle having a diameter of 860 μm. In addition, print speed and pneumatic flow pressure were set at 5 mm/s and 300 kPa, respectively. The material deposition was laminar and highly viscous on an unheated glass substrate. Subsequently, the fabricated scaffolds were oven-sintered at 37 °C. It was observed that the compression modulus of the scaffolds decreased with an increase in the HA concentration, while an increase in amylose content led to an increase in the scaffold stiffness. The outcomes of this work pave the way for the fabrication of complex, mechanically robust composite bone tissue scaffolds with tunable medical and functional properties.
Flaw Detection in Wire Arc Additive Manufacturing Using In-Situ Acoustic Sensing and Graph Signal Analysis
Authors: Bevans Benjamin , Ramalho André , Smoqi Ziyad , Gaikwad Aniruddha , Santos Telmo G. , Rao Prahalad , Oliveira J. P.
Published: September 2023

The goal of this work is to detect flaw formation in wire arc additive manufacturing (WAAM). This process uses an electric arc as the energy source in order to melt metallic wire and deposit the new material, similar to metal inert gas (MIG) welding. Industry has been slow to adopt WAAM due to the lack of process consistency and reliability. The WAAM process is susceptible to a multitude of stochastic disturbances that cause instability in the electric arc. These arc instabilities eventually lead to flaw formation such as porosity, spatter, and excessive deviations in the desired geometry. Therefore, the objective of this work is to detect flaw formation using in-situ acoustic (sound) data from a microphone installed near the electric arc. This data was processed using a novel wavelet integrated graph theory approach. This approach detected the onset of multiple types of flaw formations with a false alarm rate of less than 2%. Using this method, this work demonstrates the potential for in-situ monitoring and flaw detection of the WAAM process in a computationally tractable manner.
Sustainable 3D Printing of Organ Replica for Endoscopy Training and Medical Research
Authors: Linke Barbara , Fashanu Felicia , Bashayan Kholoud , Thavi Riddhi , Roeth Anjali A.
Published: September 2023

Additive manufacturing allows wide design freedom and manufacturing of complex parts. For the medical sciences, the fabrication of realistic and patient-specific 3D replica of organs offers exciting opportunities. Organ replicas allow better training, e.g. in endoscopy, open more avenues for medical research and can reduce the need for animal testing. However, the use of plastics for 3D printing inherently produces waste and needs to be considered with respect to a circular economy.

With the example of the upper half of a stomach replica for endoscopy, we showcase the feasibility of using recycled versus new polylactic acid (PLA) versus algae-based PLA as printing materials in a wire extrusion process. Furthermore, the stomach half replica is manufactured with elastic materials by stereolithography and polyjet binding, with the aim of improving the user experience and making the stomach model properties more realistic. This paper discusses printing energy, part dimensions and surface roughness, material recyclability, and waste in the context of the digital thread to enable more sustainable 3D printing practices for 3D organ replicas and a circular economy. We furthermore address post-processing of the 3D printed parts and usability in the context of medical training and research. This is a small case study which will be expanded in the future.
Sustainable Product Design Decision-Making Through Integrated Risk Likelihood and Impact Analyses
Authors: Enyoghasi Christian , Badurdeen Fazleena
Published: September 2023

Various decision-making methods are available for identifying sustainable designs that meet desired performance objectives. When any such method is used and a selected design is launched in the market, numerous uncertainties can affect its total lifecycle performance, giving rise to different risks that can impact expected performance. These potential risks must be identified, evaluated for possible impact, and suitable countermeasures considered, if necessary, prior to selecting any product design. The risks can be measured by their probability of occurrence (likelihood) and consequence when occurred (impact). Risk assessment literature, however, mostly focuses on developing tools and methods to analyze the probability of risks during product design decision-making. No emphasis has been laid on methods for impact analysis in the event of risk occurrence. There is also a marked lack of literature combining quantified likelihood and impact of risks for decision-making. In this paper, an approach to integrate risk likelihood results and findings from risk impact analysis is presented to facilitate better sustainable product design decision-making. Risk identification, likelihood, and impact analyses are conducted following ISO 31000 Risk Management Guidelines. Then two operational risk indices, one for likelihood and another for impact, are defined to consolidate the likelihood and impact of a design(s) on performance objectives, respectively. A Risk Level Quadrant is then developed to visualize the variation of risk impact and likelihood for different designs and identify a suitable design. An industrial case study is used to demonstrate the use of these indices for a set of Pareto design solutions identified through multi-objective optimization. The result shows that these metrics and the RLQ simplify understanding the risk levels of alternate product designs and help to make better design choices.
An Inexpensive 3D Printing System for Functional Inks Used In Electronics and Bio Applications
Authors: Thakkar Achint , Jamghare Ritik , Mishra Ravi , Emon Omar Faruk
Published: September 2023

Numerous extrusion-based 3D printing processes for electronics and bio-applications have been reported in the past decade. However, these direct ink writing (DIW) systems are mostly expensive and complex to build. Here, we report an inexpensive and open-source extrusion-based 3d printer that could be employed for printing functional inks, especially for various electronics and bio fabrication. A low-cost fused filament fabrication (FFF) 3D printer was modified to build the DIW system. An extrusion mechanism was developed with a stepper motor, a lead screw, a syringe-plunger system, and spur gears. The existing FFF heated extruder was replaced by a new extrusion mechanism. The printer was utilized to print thermosetting viscous pre-polymers. A photocurable resin was thickened using fumed silica to induce non-Newtonian shear thinning properties, and it was used for printing experiments. G-code for printing was generated using an open-source slicer software. Different extrusion rates were examined by controlling the extrusion motor rotation and speed. Also, various print parameters were investigated such as travel speed, ink viscosity, and nozzle size. The dimension of the printed geometry was studied with the change of print parameters. The printed structures were photocured using ultraviolet light. The printed geometries before and after curing were compared. To check printability for electronics, a soft pressure-sensitive membrane was 3D printed using the developed system. An acrylate-based monomer was mixed with a photoinitiator, crosslinker, fumed silica, and ionic liquid to prepare the functional ink for sensor fabrication. The printed sensor was tested under different load conditions.
Physics-Based Feedforward Control of Thermal History in Laser Powder Bed Fusion Additive Manufacturing
Authors: Riensche Alexander , Bevans Benjamin , Smoqi Ziyad , Yavari Reza , Krishnan Ajay , Gilligan Josie , Piercy Nicholas , Cole Kevin , Rao Prahalada
Published: September 2023

We developed and applied a model-based feedforward control approach to reduce temperature-induced flaw formation in the laser powder bed fusion (LPBF) additive manufacturing process. The feedforward control is built upon three basic steps. First, the thermal history of the part is rapidly predicted using a mesh-free graph theory model. Second, thermal history metrics are extracted from the model to identify regions of heat buildup, symptomatic of flaw formation. Third, process parameters are changed layer-by-layer based on insights from the thermal model. This technique was validated with two identical build plates (Inconel 718). Parts on the first build plate were made under manufacturer recommended nominal process parameters. Parts on the second build plate were made with model optimized process parameters. Results were validated with in-situ infrared thermography, and materials characterization techniques. Parts produced under controlled processing exhibited superior geometric accuracy and resolution, finer grain size, and increased microhardness.
A Fringe Pattern Analysis Technique for Photomask Line-Edge-Roughness Characterization
Authors: Wang Zhikun , Lu Kuan , Lee ChaBum
Published: September 2023

Line-edge roughness (LER) characterization is vital in modern semiconductor industry. An EKEI (enhanced knife edge interferometry)-based method for photomask LER characterization, being capable of a 0.01μm LER measurement accuracy, was proposed in this paper. The changes in fringe pattern caused by edge roughness were derived and analyzed through cross-correlation index. A negative relationship between the cross-correlation and the LER value was observed. The results are validated by both simulation and experiment, indicating that the proposed method can detect both roughness changes and residual pollution on photomask edge.