bluuebunny/crossref_metadata_2025 huggingface dataset:
Innovative Lightweight Compression System Based on Axial-Centrifugal Contra-Rotating Concept: Pushing the Limits
Authors: Kumar Akchhay , Mistry Chetankumar , Kumar Sankar , Pratap Ajay
Published: September 2023

An innovative lightweight compression system presented could push the limits and ramp up the capabilities of modern gas turbines. This system integrates the two established multi-stage compressor architectures. Firstly, the widely prevalent axial-centrifugal compressor is the configuration with several axial compressor stages with a back-end centrifugal impeller. Secondly, the contra-rotating compressor is a stator-less configuration with two sets of counter-rotating rotors. In the present study, this configuration is adopted for a small and compact compressor stage with three rotors. These are two counter-rotating front and rear axial-flow rotors and one back end centrifugal impeller rotating in the same direction as the rear axial-flow rotor. Moreover, two special annular duct arrangements, i.e. inter-stage connecting duct and centrifugal diffuser-duct were configured for aerodynamic matching of the stage and effective diffusion of flow respectively. The challenges of the present problem are manifold which comprises components such as axial-flow compressors, a centrifugal compressor, an inter-stage connecting annular duct, and a curved diffuser-duct along with the concept of contra-rotation. Multiple design innovations were performed to create an overall lightweight and compact compression system. In this work, the design approach to the proposed compressor stage and its components operating at low-speed and low-mass flow is presented. Subsequently, the numerical results performed with Computational fluid dynamics (CFD) analysis to improve the design performance iteratively are discussed. The baseline design of the contra-rotating axial compressor was configured with a higher aerodynamic loading of the front rotor and lower aerodynamic loading of the rear rotor, the rear rotor rotating at a higher design speed than the front rotor and low aspect-ratio blades. The baseline design of the backend centrifugal compressor was configured with diffusing passage shape of the diffuser-duct with a critical hub surface modification producing overall improved flow characteristics.
Rotating System Control Using Hybrid Active Bearings
Authors: Alves Diogo S. , Bailey Nicola , Keogh Patrick
Published: September 2023

Strategies to control rotor dynamic behavior are critical to achieve improved performance of rotating machinery. It is possible to control the dynamics of a rotating system through the bearing characteristics, i.e., changing their damping and stiffness coefficients. Bearings that can be commanded to change their characteristics over time are known as active bearings. Because active bearings have a complex design, their use in commercial machines is limited. In this scenario, journal bearings are still regularly used since they can provide damping and high load carrying capacity. Moreover, by modifying the fluid film thickness or clearance, one can control the dynamic behavior of the bearing, which is not a simple task when a traditional geometric format is used. However, since the fluid film thickness is proportional to the axial position of the shaft in conical bearings, their dynamic characteristics could be manipulated through compensation of the shaft’s axial position via a thrust magnetic bearing. Therefore, this paper proposes an alternative hybrid bearing design, which consists of a conical fluid-film bearing and a thrust magnetic bearing. The magnetic bearing is used to sustain the axial force created and actuate the system. For the system analyzed, the new concept was able to reduce the maximum lateral vibration of the rotor by 30%.
Teaching Optimization of Thermal and Fluid Machinery in the Post-Pandemic Era
Authors: Vouros Stavros , Diamantidou Dimitra-Eirini , Kyprianidis Konstantinos
Published: September 2023

Higher education has been crucially impacted by the pandemic during the past years. Despite the associated challenges, a wide portfolio of digital literacies has been developed for the delegates. This work evaluates the introduction of digital tools into in-person education. The “Process Optimization” course at Mälardalen University is reformed to operate in a digitally enhanced classroom mode. The course covers a variety of optimization methods applied on thermal and fluid machinery such as systems of compressors, pumps and heat exchangers, heat and power plants, aircraft trajectories and propulsion systems. The constructive alignment is presented to illustrate links between learning objectives, learning activities, and assessment tasks. A series of digital tools is introduced to elevate learning experience prior, during, and after class time. Those comprise digital quizzes, a video channel, polls, a digital whiteboard, and a digital forum. The course is systematically instrumented, yielding a vast set of statistics for evaluating the effectiveness of digital tools as well as engagement levels for learners. The contribution of digitalization into standardizing the formative and summative assessment is discussed. It is observed that digital tools complement the participation into pre- and post-classroom activities. An interactive and digitalized course evaluation activity is also designed. This allowed learners and educators to productively exchange feedback in an inclusive manner. The accrued data provides insight into the impact of digitalization on the delivery of an applied engineering course. Lessons learnt comprise quantitative and qualitative outcomes arising from the perspectives of both learners and teachers. Guidelines and recommended practices are provided for the penetration of digital tools into synchronous and asynchronous learning activities. This paper identifies opportunities as well as space for improvement arising from the penetration of digital tools into the new era for education.
Ignition of a Safran’s Helicopter Engine With a Compact Nanosecond Laser System
Authors: Maillard Martin , Amiard Hudebine Gabriel , Orain Mikaël , Doublet Pierre , Beaure D'augères Patrick , Berat Claude , Viguier Christophe , Douillard Stéphane , Freysz Eric
Published: September 2023

We report on the ignition of a Safran’s helicopter engine using a compact laser system. The laser system delivers nanosecond infrared pulses at a high repetition rate which energy can be up to 40 mJ. The first tests were run on a Safran Helicopter Engines experimental bench operating at room temperature and ambient pressure with jet A-1 fuel. We studied in detail the impact of the laser pulse energy and the spark position on the engine ignition domain. An optical focusing system fixed on the engine casing enables to focus the laser pulse at different positions in the combustion chamber. The focused laser beam generates a plasma in the combustion chamber, which ignites the engine. Our experimental data show that the laser spark position impacts the pulse energy required to ignite the engine. At the optimal position, we very reliably ignite the engine with a pulse energy of only 3 mJ. To understand this behavior, similar experiments were run on the MERCATO experimental bench at ONERA (the French aerospace lab). This bench faithfully reproduces the geometry and the flow field of the Safran engine’s combustion chamber. Using a Mie scattering imaging technique, we studied the kerosene spray generated by the start injector. Our data indicates that depending on the laser spark position in the combustion chamber, the kerosene droplets scatter more or less the laser light. This impacts the pulse energy and its spot size at the focal point and influences the laser ignition probability. In addition, ignition success requires a minimum density of kerosene droplets. Hence, the optimal laser spark position is a compromise between the droplet density at the focal point and the laser beam scattering induced by droplets before reaching that position.
Optimum Coupling of Thermal Energy Storage and Power Cycles
Authors: Guccione Salvatore , Trevisan Silvia , Guedez Rafael
Published: September 2023

The present work proposes a methodology that enables decision-making in selecting the adequate power cycle and Thermal Energy Storage (TES) type for a wide range of operating temperatures between 380 and 1200 °C. A broad spectrum of power block configurations has been explored including steam Rankine, gas turbine, supercritical CO2, (sCO2) combined gas turbine with Rankine, and combined gas turbine with sCO2. The study also evaluated molten salt, particle, and air packed bed TES to identify the most cost-effective power cycle and TES combination. A techno-economic optimization has been conducted aimed at minimizing the Levelized Cost of Storage (LCOS) for different plant capacities and charging costs. Results show that coupling of a sCO2 power block with recompression and intercooling with a particle TES is the most cost-effective solution for a 100 MWe plant with 12 hours of storage and a charging cost of 50 EUR/MWh. This achieved an LCOS value of 154.7 EUR/MWh at 750 °C with a 200 °C temperature difference. Particle-based energy storage is the most cost-effective option for a wide range of temperature combinations, while an intercooled sCO2 power block with an air-packed bed TES should be preferred when electricity is free, and storage represents a significant portion of the capital cost. Molten salt TES is the optimal choice provided that the design temperatures align with the limitations of the salts.
Trailing Edge Erosion Prevention in Steam Turbine Last Stage Rotating Blades
Authors: Sürken Norbert , Hofbauer Alexander , Pfaller Dirk
Published: September 2023

In recent years, the operational requirements for steam turbines used for heat and/or power applications have changed significantly. Especially, highly flexible operation regimes and extended operating ranges are required including frequently requested start-stop cycles and “parking” of units at low load conditions. Here, low load operation potentially comes with a set of availability relevant aspects for the low-pressure steam turbine’s last stage rotating blade row such as pronounced blade vibrations at windage or trailing edge erosion.

Unlike the well-understood leading-edge erosion of last stage rotating blades in steam turbines, trailing edge erosion is a phenomenon which in the past was nearly exclusively known from steam turbines for district heating power plants and some industrial applications. With the intensified flexible operation of power plants, however, trailing edge erosion is more likely to be observed also for non-extraction units.

It is assumed that trailing edge erosion occurs during windage operation, when the flow through the last stage is low enough such that the recirculation vortex in the exhaust area transports moisture back towards the trailing edge of the last stage rotating blade. The subsequent water impingement eventually may cause material degradation [1] at a mechanically loaded area of the blade’s foil above the root plate. Sources of moisture can be, e.g., inherent steam wetness or water injection systems.

To enable an estimation of trailing edge erosion susceptibility for certain applications and load conditions, an evaluation scheme is proposed in the present paper. Its objective is to indicate and detect the built-up of trailing edge erosion early enough to enable a timely and pre-emptive condition-based service intervention and/or to advise a change in operation mode, as applicable.

The developed evaluation scheme is subsequently implemented into a Combined Heat and Power Plant featuring an extraction machine. The resulting inspection results substantiate the potential trailing edge erosion prevention capability of the developed scheme.
Effect of Coolant Flowrate on High-Pressure Turbine Tip Flow Structures and Thermal Loading
Authors: Christensen Louis , Celestina Richard , Sperling Spencer , Mathison Randall , Aksoy Hakan , Liu Jong , Nickol Jeremy
Published: September 2023

Film cooling is essential to operation of modern gas turbine blades, which can operate at temperatures exceeding the working limits of the materials they are made of. The tips of turbine blades are an area of keen interest where there can be high thermal loading from tip leakage flows, and, in the case of squealer tips, it can be difficult to effectively cool these areas. The naïve approach to reducing thermal loading is to increase the amount of coolant supplied to the blade. This approach is intuitive however the increased level of coolant issued from the blade affects flow structures around the blade altering how the heat transfer is occurring and ultimately affecting the thermal loading. This work studies a contemporary cooled high-pressure gas turbine tip with a squealer rim at various coolant flowrates. Conjugate heat transfer simulations informed from short duration turbine tests operating at scaled engine conditions are used to investigate the effect of coolant flowrate on the turbine blade tip flow field and thermal loading.

Variation of the coolant flowrate does not cause macroscale changes to the flow structures, as the introduction of film cooling does, but rather these variations make small yet significant changes to the interactions between the vortex structures and coolant jets that can be beneficial or detrimental to the thermal loading on the blade tips. Additionally, not all regions of the blade tip are impacted by changes to the coolant flowrate; different areas of the blade can reach a coolant saturation level where further addition of coolant is ineffective. Results from this work present a more complete picture of the complex effects film cooling has on turbine blade tip flows. Knowledge of the unintuitive and sometimes paradoxical effects of cooling can be used to further optimize film cooling schemes.
Usage of an Interactive Learning Platform in Project-Based Graduate Courses for the Preliminary Design of Axial Turbines
Authors: Gomes Dias Marcelo Marques , Tozi Luiz Vitor , de Oliveira Silva George Patton , Tomita Jesuino Takachi , Bringhenti Cleverson
Published: September 2023

The industry and the academy are continuously developing new approaches, technologies, and models for gas turbine design. However, there was not enough time to cover all the relevant subjects for undergraduate or graduate students in one or two-semester courses. So, in previous works, the authors described a developed interactive platform for the preliminary design of multistage axial flow turbines for uncooled blades and improved it based on the student’s feedback, so it could be as didactic as possible. Its application in the courses offered by the Turbomachines Department at Aeronautics Institute of Technology (ITA) successfully accelerated the learning process of the basics. In the graduate courses, the use of the program granted time to more complex topics, e.g., blade cooling, off-design performance, CFD simulations, manufacture, and machine learning applied to turbomachine design, which were not covered in previous years. The program initiates with the data from thermodynamic cycle calculation and the definition of the main design parameters. Then, it computes the aerothermodynamic properties of the flow stage-by-stage, from hub to tip, and the geometry of the blades. Finally, it estimates the losses by source, iteratively, through the models of Ainley and Mathieson [1], Dunham and Came [2], or Kacker and Okapuu [3]. This work presents some studies performed by the students using the platform. Firstly, it was varied some design key parameters such as loading and flow coefficients, the aspect ratio and the pitch-to-chord ratio of the blades, the airfoil section geometry, and the tip clearance, once at a time while maintaining the others. Then, it was possible to observe how these modifications affected the number of stages required, the stress levels, the machine size, and the isentropic efficiency, tracking the primary sources of loss. After, the students implemented other loss models, such as the one by Craig and Cox [4], aiming to analyze the effect of surface roughness on the losses. Finally, they compared the platform results with CFD simulations and experimental data from turbines developed at the Department. The paper concludes with the students’ insights through the project and comments on how the employed methodology improved their learning process.
Design and Cooling Performance of Additively Manufactured Ceramic Turbine Vanes
Authors: Fox Andrew , Lynch Stephen , Young Jason C. , Frick Carl P. , Hankins Jennifer , Kuhn Kyle , Brinckmann Stephan A. , Fertig Ray S.
Published: September 2023

Ceramic materials are of significant interest in aviation and power generation gas turbine engines due to their low density and ability to withstand high temperatures. Increased cycle thermal efficiency and higher specific power output is possible by incorporating ceramic components that enable high turbine inlet temperatures and lower required cooling airflow levels. However, ceramics can be difficult and costly to form into the complex shapes used in gas turbine components, often requiring specialized multi-step processes. Furthermore, ceramic components in the hottest areas of a gas turbine, such as vanes or blade shroud seals, will still likely require cooling which is challenging to implement in conventional ceramic manufacturing approaches. Therefore, this study presents a multidisciplinary approach that investigates the design, fabrication and overall cooling effectiveness evaluation of additively manufactured (AM), polymer derived ceramic (PDC) turbine vanes. A thermo-mechanically optimized vane design was generated, ceramic additive manufacturing of the complex cooling configuration was developed, and quantification of the increase in overall cooling effectiveness was performed in a 1X scale, high-speed facility using infrared thermography. This study produced a PDC AM process, capable of printing complex internal cooling schemes in 1X scale turbine vanes. It was found that the optimized vane more than doubled the overall cooling effectiveness observed in the baseline design, which reasonably agreed with thermomechanical optimization model predictions. Additionally, the optimized ceramic vane outperformed an identical metal vane, in terms of area averaged cooling effectiveness, suggesting that the ceramic vane could operate at reduced coolant flow rates to achieve comparable levels of cooling performance.
Progress Toward Climate-Friendly Aviation in the ARPA-E ASCEND and REEACH Programs
Authors: de Bock H. Peter , Tew David E. , Rahman Zaiur , Lecoustre Vivien , Cox-Galhotra Rosemary A.
Published: September 2023

The decarbonization of commercial aviation in the coming decades represents a formidable challenge. For ranges of less than several hundred miles, all-electric battery-powered aircraft have the potential to be attractive solutions. However, for longer ranges, the appreciably greater specific energy of fuels will continue to be required. Nevertheless, our climate crisis mandates that these fuels must be synthesized in a carbon-neutral manner, and consequently, they are likely to be considerably more expensive than their fossil-derived counterparts. These challenges will result in even more impetus to make future propulsion systems more efficient — regardless of whether that energy is contained within batteries or fuels. Electrified propulsion systems are potential enablers for our transition to this future through their ability to facilitate the integration of disparate storage and conversion technologies into a single hybrid system that offers high conversion efficiency at an acceptable weight. In this paper, progress made in the development of such systems within the ARPA-E ASCEND and REEACH programs is described.
Effect of Hot Gas Path Component Corrosion on the Performance of Hydrogen Fueled Micro Gas Turbines
Authors: Hashmi Muhammad Baqir , Mansouri Mohammad , Breuhaus Peter , Lemma Tamiru Alemu
Published: September 2023

Micro gas turbine (MGT) is a promising technology for decentralized energy systems because of its wide range of benefits, such as fuel and operational flexibility, power density, combined heat and power efficiency, and lower emission levels as compared to its conventional counterparts. The stringent climate policies to overcome challenges caused by global warming demand significant measures including use of alternative fuels. Among low emission fuels, hydrogen might pose several challenges owing to its distinct chemical and physical properties. One of the potential challenges is the significant changes in exhaust gas fluid properties, such as relatively enhanced level of steam/moisture content in the flue gas. The varied exhaust gas fluid properties might generate both thermal stresses and considerable wet corrosion in the turbine section of gas turbine. This challenge becomes more susceptible in retrofitted gas turbines where combustor is replaced, while the rest of the turbomachinery remains same. Therefore, hot gas path components of gas turbines may face health degradation and subsequent performance deterioration and reduced lifetime.

The aim of this paper is to compare the effect of injected corrosion faults on the thermodynamic performance deterioration of both H2 and natural gas (NG) fueled MGT. In this regard, this study first presents an experimentally validated simulation model of a 100 kW MGT using a commercially available software tool, GasTurb. The study compares the thermodynamic and combustion flue gas properties of both hydrogen and NG fueled MGT at full load conditions. The combustion reactions and detailed analysis of fluid flow properties manifested that H2 fuel utilization results in an increased steam content (by ∼106%) as compared to NG combustion. The combined effect of turbine corrosion severity level and high ambient temperature on the overall performance of the MGT is also studied. The study shows that the increased corrosion severity level at high ambient temperature can lead to deterioration in power and thermal efficiency. The findings of the present study might be helpful in designing new hot gas path components, and fuel accessories to upgrade the existing fleet of MGTs, while using hydrogen-rich fuels resulting in enhanced performance, and reliability.
GPU-Accelerated Implicit Turbomachinery Flow Solver Using Multiple MPI Communicators
Authors: Wang Feng , di Mare Luca
Published: September 2023

This paper describes a procedure to port an unstructured CFD solver to GPU for turbomachinery simulations via NVIDIA OpenACC. Matrix-free implicit time stepping is used for robust and efficient time integration. Data movement between the device and the host is managed explicitly and is minimized for optimal performance. For multiple GPU computations, a flexible multistage decomposition is devised. The computational domain is first divided into different components (or sub-domains), each of which represents an physical entity, such as a bladerow. For each subdomain, a graph partition is then performed. Data exchange among multiple GPUs are devised to accommodate such domain decomposition strategy. For halo exchange within each sub-domain, data can be sent directly from one GPU to the other one if permitted by the hardware. To exchange data among different sub-domains, a general purpose coupler is devised to exchange data among the GPUs via the host. In terms of computational speed, for a socket-to-socket comparison (one V100 and 20 CPU cores), the GPU code shows a global speedup of 8.1 for double precision and 10.1 for single precision. Furthermore, the GPU code is 5.5 and 6.9 times more energy efficient for double and single precisions, respectively. The GPU code is validated on Rotor 37 and a high speed multistage compressor. Good agreement with rig data is observed for both cases. The multistage compressor case has roughly 17 million cells and it takes the GPU code 8 hours to produces 4 revolutions using 4 V100. The developed GPU code represents a flexible computational framework for future multi-fidelity/physics simulations on heterogeneous computing environment.
Centrifugal Compressor Polytropic Performance Evaluation: Taher-Evans Methods
Authors: Taher Matt , Evans B. F.
Published: September 2023

The polytropic compression process is defined as a reversible and non-adiabatic process, in which the ratio of useful compression work to the change of enthalpy remains constant along the polytropic compression path. Unlike an isentropic process, the polytropic process accounts for unavoidable degradation of energy as governed by the second law of thermodynamics. Polytropic efficiency can be very accurately calculated by numerical integration along a defined path or by much less accurate, older polytropic exponent methods in a closed form solution.

The Taher-Evans numerical integration methods for the calculation of polytropic performance of centrifugal compressors are based upon a constant efficiency, temperature-entropy polytropic path represented by a mathematical model employing cubic polynomials.

In earlier papers published by the authors on Taher-Evans methods, the maximum relative deviation limit used for judging solution certainty of the calculation of the polytropic efficiency and polytropic work was chosen as ≤ 0.001% to show the high accuracy of Taher-Evans methods. The uncertainties associated with the realities of measured test data to determine a fluid’s thermodynamic and thermophysical properties using equations of state, however, may impose constraints on the overall accuracy for the calculation of the polytropic efficiency and the polytropic work in factory or field performance testing of centrifugal compressors in accordance with ASME PTC-10. In this paper, the use of Taher-Evans methods is explained for the factory and field test conditions that are required to achieve a relaxed maximum relative deviation limit ≤ 0.01% for reporting the calculation of the polytropic efficiency and polytropic work. For ASME PTC-10 type 1 and type 2 tests, this paper presents the selection criteria for the maximum number of sequential Taher-Evans cubic polynomial segments needed to achieve target relative deviations of either 0.001% or 0.01%.

Example cases confirm that the Taher-Evans cubic polynomial methods yield highly accurate results while requiring fewer computing resources and reducing computing elapsed time compared with other endpoint or multi-step numerical methods. Also, a new relationship with a condensed expression is developed to precisely calculate the real gas polytropic volume exponent at each point along the polytropic path.
Additively Manufactured NiTiHf Shape Memory Alloy Transformation Temperature Evaluation by Radial Basis Function and Perceptron Neural Networks
Authors: Abedi Hossein , Abdollahzadeh Mohammadjavad , Almotari Abdalmageed , Ali Majed , Mohajerani Shiva , Elahinia Mohammad , Qattawi Ala
Published: September 2023

Employing Laser Powder Bed Fusion (LPBF) method to manufacture NiTiHf Shape Memory Alloy (SMA) is becoming more common. The major design property for NiTiHf is the transformation temperatures (TTs) which control the activation threshold of the SMA material and enable it to create the shape change due to a microstructure phase transformation. Given the high number of fabrication factors, machine learning (ML) approaches provide a promising approach to the design of SMA to control the TTs.

The main obstacle to using ML methods is the need for an established correlation between fabrication features and material properties. The presented work develops an ML approach to enable the prediction of the TTs for additively manufacturing NiTiHf. The work uses all available experimental data on additively and conventionally manufactured NiTiHf. Selected fabrication features included in the ML models consider the elemental compositions of NiTiHf, laser power, laser speed, hatch spacing, and almost all the processing steps historically used to manufacture, or heat treat the NiTiHf for SMA.

Multiple models of Multi-Layer Perceptron (MLP) and Radial Basis Function (RBF) Neural Networks (NN) are developed to predict the TTs of LPBF-manufactured NiTiHf. The models successfully predict the TTs for various NiTiHf fabrication conditions.
Systemic Control of 3D Bioprinting Process Parameters to Achieve Defined Scaffold Porosity
Authors: Quigley Connor , Tuladhar Slesha , Adhikari Samrat , Habib MD Ahasan
Published: September 2023

Due to its inbuilt ability to release biocompatible materials encapsulating living cells in a predefined location, 3D bioprinting is a promising technique for regenerating patient-specific tissues and organs. Among various 3D bioprinting techniques, extrusion-based 3D bio-printing ensures a higher percentage of cell release, ensuring suitable external and internal scaffold architectures. Scaffold architecture is mainly defined by filament geometry and width. A systematic selection of a set of process parameters, such as nozzle diameter, print speed, print distance, extrusion pressure, and material viscosity, can control the filament geometry and width, eventually confirming the user-defined scaffold porosity. For example, carefully selecting two sets of process parameters can result in a similar filament width. However, the lack of availability of sufficient analytical relations between printing process parameters and filament width creates a barrier to achieving defined scaffold architectures with available resources. In this paper, filament width was determined using an image processing technique and an analytical relationship was developed, including various process parameters to maintain defined filament width variation for different hydrogels within an acceptable range to confirm the overall geometric fidelity of the scaffold. Proposed analytical relations can help achieve defined scaffold architectures with available resources.
Review of Interventional Robotic Systems
Authors: Liu Yang , Li Dian-Ru
Published: September 2023

The success of the da Vinci system has shown the feasibility and a great potential of using robotic systems to improve healthcare. With a trend of replacing more and more invasive surgeries with minimally invasive interventional procedures, developing robotic systems for interventions has seen a boost of interest from both the industry and the academia in the past two decades. Using robotics to conduct intervention procedures is expected to better protect the clinicians by reducing their radiation exposure and to create better patient outcome in cases where high positional accuracy is needed, such as placing a stent or a coil. However, adoption of interventional robotics has been slow due to the limitations of current interventional robotic systems such as a steep learning curve, lack of haptic feedback, and safety concern. This narrative review first introduces the current clinical applications of interventional robotic systems and their limitations. The major technological features of interventional robotics, including the master-slave manipulator, soft continuum robot, and end effector, are then described. Finally, several manufacturing research topics are proposed for future interventional robotic systems.
Powder-Binder Interaction in Binder Jetting Process: A Simulation Study on Bimodal Powders
Authors: Shahed Kazi Safowan , Manogharan Guha
Published: September 2023

Binder Jetting (BJT) is a room-temperature powder-bed additive manufacturing process suitable for a wide range of materials such as bioceramics, sand, metals, and polymers. In this process, powder-binder interaction, which is influenced by the powder bed packing density during the printing process, has a major impact on the overall part quality. Although few recent studies have explored the modeling of the binder-jetting process, they are not realistic (e.g., 200 % larger droplet size when compared to the actual process). This study is the first to report a systematic study into the powder-binder interactions for bimodal powders with actual binder-jetting conditions across a wide range of packing densities and binder-jetting conditions. This integrated Discrete Element Modeling (DEM - powder spreading) – VOF (Volume of Fluid - binder interaction) study analyzed the powder-binder interaction in terms of: penetration depth, spreading time, and area per droplet on the powder bed. It was observed that an increase in droplet velocity resulted in deeper penetration (5.4%) of the binder but reduced the area of spread (20.8%) across packing densities. In addition, for a given droplet size and packing density, an increase in droplet velocity resulted in a shorter spreading time (27.3%). Findings from this study provide a new understanding of the temporospatial characteristics of the binder-powder interaction, which helps in identifying optimal printing parameters for a bimodal powder feedstock.
Effect of Blown Powder Directed Energy Deposition Angle On Overspray Contamination
Authors: Heinrich Lauren , Kannan Rangasayee , Burl Alan , Nandwana Peeyush , Fillingim Kenton , Feldhausen Thomas , Kurfess Thomas , Saldaña Christopher
Published: September 2023

Blown powder directed energy deposition (DED) hybrid machine tools are particularly beneficial when the net shape of a component is to be manufactured in an additive and machined interleaved fashion. This investigation seeks to analyze the effect of the additive head lean angle relative to the part on blown powder DED surface contamination due to overspray. These hybrid DED platforms are commonly installed on multi-axis machining systems where the lean of the deposition head relative to the component surface can be controlled by tilting the component. The blown powder DED process has a 10–50% lower catchment efficiency as compared to wire fed DED systems. This excess powder is still fed towards the deposition location where the particles are heated by the laser and rebound off the melt pool. Some of these heated particles impact the previously machined thin-wall surface. While the deposition process and tool path planning process has been evaluated, the effect of the overspray due to lean angle of the deposition head on the previously thin-wall machined surface is not yet fully understood. This investigation found that minimum lean angle coincides with minimal overspray effect with nearly no contamination. If a lean angle is required, the maximum lean angle possible should be implemented for the smallest effected overspray area on the machined surface which was found to decrease the affect zone by half compared to intermediate lean angles. A diameter divergence was also noticed as the deposition angle was increased. In this study, a thorough analysis of the surface and geometric effects when depositing thin-walled components at varying angles is completed. It has been shown that part quality can be significantly affected by lean angle and thus must be incorporated as an additional design consideration in the manufacturing process.
Laser Welding With and Without Filler Wire of Aluminum Thin Sheets in Different Semi-Finished Formats
Authors: Perez Zapico Eriel , Ascari Alessandro , Liverani Erica , Fortunato Alessandro , Dimatteo Vincenzo
Published: September 2023

Laser welding of aluminum sheets gained an increased interest in the last few years, especially for the production of lightweight components. One of the most critical factors to be taken into consideration in this particular application is the formation of pores in the fused zone, that strictly depends on the semi-finishing format of the parent sheets. In particular, in fact, when one or more parts are produced by means of high-pressure casting or additive manufacturing, this phenomenon is amplified and optimization of process strategies and parameters is of utmost importance for achieving a sound joint. According to these considerations the present paper deals with welding of AA6082 sheets with additively manufactured AlSi10 ones in a configuration that is typical for the production of battery cases for the e-mobility field. In order to understand the role of process strategies on weld bead quality, both autogenous welding and welding with filler wire are investigated and the eventual benefits of applying a wobbling beam shaping is also considered. For any of the above-mentioned strategies, the role of process parameters, such as laser power, welding speed, filler wire speed and wobbling, is investigated, with particular reference to the formation of pores and defects. Porosity is analyzed as the main driver for the definition of weld bead quality and also weld bead shape and geometry are analyzed.
Additive Insert Molding (AIM) – A Practical Paradigm for Mass Customization of Multi-Material/Functional Parts
Authors: O'Quinn Ryan , Pradeep Sai Aditya , Pilla Srikanth , Farahani Saeed
Published: September 2023

Additive and traditional manufacturing are often regarded as separate schools of thought in end-part production, each with its own advantages and shortcomings. However, several attempts have been made to combine these two approaches in a complementary manner to improve upon their respective downfalls. Motivated by this approach, this work introduces a new integration concept that combines the best-in-class plastic manufacturing process, injection molding (IM), with additive manufacturing (AM) through a hybrid manufacturing process, which is here called Additive Insert Molding (AIM). AIM is the process of additively manufacturing inserts, placing the inserts into a specialized tool for a subsequent injection molding process, and finally ejecting a single hybrid part out of the tool. By this integration, the customizability and geometric freedom of AM are combined with the reliability and high production rate of the IM process. This integration also facilitates the incorporation of multi-material and part consolidation design approaches, hence hypothesizing AIM as a promising route for cost-efficiently mass-customizing multi-material/functional parts. Besides the introduction of the AIM concept, its main benefits and application criteria are herein discussed. Three proof-of-concept case studies are then presented evaluating the feasibility of using AIM for mass personalization, tool/process simplification, and tailored reinforcement. The results of each case study are analyzed to identify the potential benefits and challenges of using AIM in real-world applications. Finally, the important remarks and future research directions are extracted and discussed at the end of this paper.
Vision-Enabled Robot-Mill Collaboration for Hybrid Manufacturing
Authors: Goodwin Jesse , Saldaña Christopher
Published: September 2023

Recently, convergent manufacturing, or the combination of multiple processes into a single system, has gained attention for potential uses in hybrid additive-subtractive manufacturing. Here, a robot-CNC machine combination is explored as a convergent solution to hybrid manufacturing. Usually, hybrid manufacturing is performed either using a sequential process where parts are moved from additive to subtractive cells or using a process where all operations occur in a single machine. A less explored solution to the hybrid machining problem is to use a combination of two machines operating on the same workpiece to complete the process, allowing for interleaved or simultaneous hybrid processing. In this work, a flexible system is presented where a 6-axis robotic arm for deposition is combined with a 3-axis CNC mill for hybrid manufacturing. With this system, the robot can be moved to and away from the CNC as needed for a flexible manufacturing framework. With the added flexibility of the system, comes the problem of robot localization. Vision based robot localization methods were implemented to address this problem, and studies were conducted to determine the effects of disturbances encountered in a manufacturing environment on the localization performance. Results show that the proposed vision system can locate the robot within .5 mm and .25 deg, causing minimal disruption to the machining process.
Mixing of Spherical Solid and Nanoporous Copper Powders As Low-Reflectance Feedstock for Laser Powder Bed Fusion
Authors: Kublik Natalya , Niauzorau Stanislau , Azeredo Bruno
Published: September 2023

Micro- and nanoporous materials have gathered attention from the scientific community due to their size dependent properties, including but not limited to high specific surface area, surface diffusivity, bulk diffusivity and permeability, catalytic activity, and distinct optical properties. In this work, spherical nanoporous copper (np-Cu) powders, due to their nanosized porosity and low Cu2O content, show hemispherical total reflectance of 20% which is significantly lower than its bulk counterpart value for solid or molten copper of approximately 97% at wavelengths of most commercial Laser Powder Bed Fusion (L-PBF) commercial machines. The low-reflectance of np-Cu powders has the potential to be used in L-PBF to improve laser absorption, volumetric energy efficiency, and throughput of this additive manufacturing process. In fact, a prepared mixture of solid Cu powders containing only 5 wt.% of np-Cu powders reflects 34.8 % less than pure copper powders as shown in this paper. Np-Cu powders are fabricated via chemical dealloying of gas atomized CuAl alloy in a robust and scalable approach, and then mixed with pure copper powders to prepare hybrid feedstocks. Under this framework, the crucial role of deglomeration strategies to achieve homogeneity and flowability of np-Cu/Cu hybrid mixtures are evaluated via particle imaging to determine agglomerate size and composition with an eye at obtaining a high-quality print in L-PBF. In np-Cu powders fabrication, washing them in low-surface tension fluids upholds the highest degree of deglomeration in their fabrication process, and for hybrid feedstocks preparation, pre-mixing Cu and CuAl prior to dealloying yields the best homogeneity results with smallest size of agglomerates and good flowability.
Full Stack Virtual Commissioning: Requirements Framework to Bridge Gaps in Current Virtual Commissioning Process
Authors: Sim Jonathan B. , Shah Kavan N. , Saez Miguel , Abell Jeffrey , Zhou Yanli , Faris John , Tilbury Dawn M. , Barton Kira
Published: September 2023

Commissioning forms a crucial part of the initiation of a new manufacturing system. Commissioning activities occur after the design of a new manufacturing system or product line, but before the system is built and deployed into production. Current commissioning practices involve virtual commissioning (VC) tools with limited verification abilities, where virtual models representing a manufacturing system are built and then used in simulation. Software-In-The-Loop (SIL) simulation is applied to virtual models to measure and verify performance metrics that are important to a manufacturer. Due to inaccuracies and gaps in current VC capabilities, physical commissioning is still a common practice for complete verification and validation of a manufacturing system prior to deployment. The need for physical commissioning requires valuable time during the commissioning process. A Full Stack Virtual Commissioning process would eliminate the need for physical commissioning, allowing system integrators to more rapidly commission new manufacturing systems. In this work, we provide an initial Requirements Framework that outlines the critical technological and research gaps that must be addressed in order to achieve a transition toward a Full Stack Virtual Commissioning process. The current state-of-the-art approaches for commissioning are presented, along with an introduction to digital twin technology as an important VC enabler that is being explored within the academic and industrial domains. Lastly we highlight key benefits, important technical gaps, and critical challenges that must be addressed in order to facilitate a transition to Full Stack Virtual Commissioning.
Integrative neurocircuits that control metabolism and food intake
Authors: Brüning Jens C. , Fenselau Henning
Published: September 2023

Systemic metabolism has to be constantly adjusted to the variance of food intake and even be prepared for anticipated changes in nutrient availability. Therefore, the brain integrates multiple homeostatic signals with numerous cues that predict future deviations in energy supply. Recently, our understanding of the neural pathways underlying these regulatory principles—as well as their convergence in the hypothalamus as the key coordinator of food intake, energy expenditure, and glucose metabolism—have been revealed. These advances have changed our view of brain-dependent control of metabolic physiology. In this Review, we discuss new concepts about how alterations in these pathways contribute to the development of prevalent metabolic diseases such as obesity and type 2 diabetes mellitus and how this emerging knowledge may provide new targets for their treatment.
A
Candida auris
–specific adhesin, Scf1
,
governs surface association, colonization, and virulence
Authors: Santana Darian J. , Anku Juliet A. E. , Zhao Guolei , Zarnowski Robert , Johnson Chad J. , Hautau Haley , Visser Noelle D. , Ibrahim Ashraf S. , Andes David , Nett Jeniel E. , Singh Shakti , O’Meara Teresa R.
Published: September 2023

Candida auris
is an emerging fungal pathogen responsible for health care–associated outbreaks that arise from persistent surface and skin colonization. We characterized the arsenal of adhesins used by
C. auris
and discovered an uncharacterized adhesin, Surface Colonization Factor (Scf1), and a conserved adhesin, Iff4109, that are essential for the colonization of inert surfaces and mammalian hosts.
SCF1
is apparently specific to
C. auris
, and its expression mediates adhesion to inert and biological surfaces across isolates from all five clades. Unlike canonical fungal adhesins, which function through hydrophobic interactions, Scf1 relies on exposed cationic residues for surface association.
SCF1
is required for
C. auris
biofilm formation, skin colonization, virulence in systemic infection, and colonization of inserted medical devices.
Ethically cleared to launch?
Authors: Rahimzadeh Vasiliki , Fogarty Jennifer , Caulfield Timothy , Auñón-Chancellor Serena , Borry Pascal , Candia Jessica , Cohen I. Glenn , Covington Marisa , Lynch Holly Fernandez , Greely Henry T. , Hanlon Michelle , Hatt James , Low Lucie , Menikoff Jerry , Meslin Eric M. , Platts Steven , Ravitsky Vardit , Ruttley Tara , Seidler Rachael D. , Sugarman Jeremy , Urquieta Emmanuel , Williams Michael A. , Wolpe Paul Root , Donoviel Dorit , McGuire Amy L.
Published: September 2023

Rules are needed for human research in commercial spaceflight
Widening the use of 3D printing
Authors: Balazs Daniel M. , Ibáñez Maria
Published: September 2023

A light-triggered fabrication method extends the functionality of printable nanomaterials
Cellular coupling in the heart
Authors: Camelliti Patrizia , Stuckey Daniel J.
Published: September 2023

Fibroblasts in scar tissue elicit myocyte excitation and promote arrhythmia in mouse hearts