bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow Disturbance by Intrusive Instrumentation: Part 1 – Protrusions on the Pressure Side of HP Compressor Vanes
Authors: Jung Daniel , Schäflein Lukas , Jeschke Peter , Wunderer Roland
Published: August 2024

In this study, we quantify the aerodynamic impact of spanwise pressure tubes located on the pressure side of a high-pressure compressor stator vane. We conducted experiments in a linear cascade wind tunnel (Mach number ∼0.5, Reynolds number 790,000) by modeling the pressure tubes as simplified protrusions with varying dimensions. Testing eight configurations with protrusion heights of 33% and 66% of the maximum vane thickness and a protrusion width ranging from 8% to 24% of the chord length reveals that narrow, as well as high, protrusions increase the total pressure loss the most. Therefore, the narrowest and highest protrusion configuration increases the loss by a factor of 4.7 compared to a vane without a protrusion, while the widest and flattest protrusion increases the loss by a factor of 1.2. Oil flow visualization and CFD simulations reveal that narrow and high protrusions lead to separation-induced losses. The study offers insights for test engineers who are responsible for designing compressor vane instrumentation to minimize additional total pressure loss.
A Large Eddy Simulation Study on Hydrogen Microjets in Hot Vitiated Crossflow
Authors: Broumand Mohsen , Yun Sean , Hong Zekai
Published: August 2024

In the present paper, the results of a large eddy simulation (LES) study on hydrogen microjets (dj ∼ 0.5 mm) injected into a hot (1600 K) vitiated crossflow at different angles — namely, normal (90°) and inclined jet (30°), are presented. The goal is to explore the effects of injection angle on coherent turbulent structure formations, flame-vortex interactions, and wall heat flux contributions. The LES identifies the presence of the horseshoe vortex, the shear layer vortices (SLV), and the counter-rotating vortex pair (CVP), along with the shedding of spanwise-symmetry hairpin vortices in both the normal and inclined jets. The structures in the latter, however, appear more convoluted. In the near field, the SLV-induced flow is found to play a key role in the mixing and flame propagation in the windward side of the jet that is stabilized through the autoignition process along the front edge of both the normal and inclined jets close to their exits. The flame-shear layer offset phenomenon is also noticed on the windward side of the jets. In the far field, the CVP is found to be the dominating mechanism in the entrainment of the hot vitiated crossflow by the reacting jet and large-scale mixing. Its induced counter rotating flow field give rises to the flame propagation and the heat and species transfer from the windward to the leeward side of the jet near the injection wall. In the wake region, the combustion and its byproducts persist in closer proximity to the jet exit of the normal case because of the presence of a much stronger recirculation zone behind the jet. Accordingly, higher wall heat fluxes are obtained in this region for the normal jet. The mean wall heat flux values of both the normal and inclined jets decrease and approach each other with moving away from the jet exit in the streamwise direction. The findings indicate that the CVP-induced flow drastically increases heat transfer to the near wall region, resulting in a spanwise-symmetry heat flux profile with double peaks in downstream. The results of the present LES study are compared to the experimental data available in the literature by considering instantaneous hydroxide (OH) fields and mean wall heat fluxes.
Investigation of Ammonia/Hydrogen Mixtures and Pilot-Split Strategies in a Laboratory-Scale Radial Swirl Combustor
Authors: Rizza Raad , Talibi Midhat , Cosway Benjamin , Kenny Lucas , Beita Jadeed , Ducci Andrea , Sadasivuni Suresh , Balachandran Ramanarayanan
Published: August 2024

The transition to a decarbonised energy future relies on identifying the most suitable alternative fuels that can meet the needs of various energy sectors. While both ammonia and hydrogen are zero-carbon energy vectors, their physical properties and burning characteristics sit on either side of that of natural gas. Hence, mixtures of ammonia and hydrogen are being increasingly looked at as having the potential to fuel current energy systems without requiring significant combustor redesign. However, the combustion characteristics and operation limits for different ammonia/hydrogen mixtures still need to be evaluated. For GT applications in particular, the effect of ammonia/hydrogen mixture composition and operating condition on flame behaviour and stability is not well understood.

The current work was carried out in a laboratory scale, radial swirl-stabilised turbulent combustor. A systematic study of two ammonia/hydrogen blend ratios (70:30 and 80:20 by volume) and a range of equivalence ratios were tested for different pilot-split ratios, to understand the effect on flame shape, stability and dynamics. Time-resolved pressure and integrated heat release fluctuations were measured to evaluate combustor dynamics, and NH2* chemiluminescence flame images were captured to understand spatial differences in flame structure. When comparing blend ratios, differences were observed inflame macro-structures and combustor dynamics, which could be largely attributed to the considerable difference in the laminar flame speeds of the blends. The addition of pilot generally improved the stability and lean operation for both blend ratios.
Characterization of a Premixed Gas Turbine Injector for Light-Duty and Low Emissions Applications
Authors: Carusotto Salvatore , Salvadori Simone , Cavalli Alberto , Casto Elisabetta , Cardile Francesco , Misul Daniela Anna
Published: August 2024

Recent trends in gas turbine combustor design aim at lowering pollutant emissions through the usage of lean premixed solutions that allow for controlling the fuel mixture and the temperature field. Modern injector-combustor systems guarantee low levels of NOx emissions thanks to the employment of premixed and swirl-stabilized flames. Such kind of solution must be designed also considering the possible use of hydrogen as fuel, thus abating emissions further. Unfortunately, this type of technology is significantly more susceptible to flashback and instability when switching to hydrogen blends. For that reason, it becomes necessary to correctly characterize the injection system before considering any possible redesign at the industrial level. In this research, a premixed injector for light-duty applications, with a relatively limited net power of around 5MW, is investigated through experimental and numerical analysis. In the experimental campaign, consisting of a series of flow tests in quiescent air, the mass flow rate associated with different expansion ratios is evaluated in terms of the equivalent area of a calibrated orifice. The obtained data are used to construct and validate the numerical fluid-dynamic models. First, the 1D model is developed with AxSTREAM® NET by fitting the available experimental data through calibrated losses in an equivalent geometrical setup and is used to obtain quick and reliable information on the mass flow rates and pressure levels at different points of the gas circuit. Second, a set of 3D CFD simulations is performed with the ANSYS® FLUENT® solver to achieve a higher level of detail in terms of fluid-dynamic characterization. In that case, the injector domain is split into two parts, the pilot and the main and the two components are analyzed by varying the expansion ratio in quiescent air to validate to numerical approach by matching pressure levels and mass flow rates. Moreover, due to the complex geometry of the main part, the main fuel circuit is divided further into two components to reduce the computational cost, then the characterization is based on an iterative procedure. The grid dependence ensures that no effect of the spatial filter is present, whereas the validation against experimental data with a maximum error of around 5% for the pilot geometry allows for obtaining fundamental preliminary information for the creation of reacting simulations setup or to proceed with the redesign of part of the injection system using additive manufacturing techniques to reduce component cost.
Optimization of a Propeller Fan for Noise and Efficiency by Using 3D Inverse Design Method
Authors: Zhang Luying , Dinh Thien Xuan , Kawakita Kenji , Riddell Alfred , Goto Akira , Zangeneh Mehrdad
Published: August 2024

In this work, a methodology for propeller fan optimization using the three-dimensional inverse design method is presented. The workflow is demonstrated through the optimization of a previously designed propeller fan, the performance of which has been numerically and experimentally studied. The vortex distribution, the pressure loading on the blade surface and the stacking were varied during the optimization. The 3D blade geometries were obtained from the inverse design calculation, which can explore a large design space with relatively small amount of input parameters. This leads to some advantages when using a design of experiments (DOE) approach. The aim is to improve the aerodynamic performance of the fan. Meanwhile, the noise level should be kept under control. A multi-objective optimization was carried out based on the DOE results to find the balance between conflicting objectives. An optimum design was picked from the optimization. The performance of the optimized design was then verified by computational fluid dynamics simulations. The results show an increase of peak efficiency and pressure rise. The low flow rate performance is also improved. The flow physics that led to the performance improvement are discussed based on the numerical results. The same optimization workflow and principles can be applied to other types of axial fan as well.
Numerical Assessment of an Aerodynamic Probe to Enable Short Focal Length Laser Diagnostics in High Temperature Supersonic Flows Based on Flow Disturbance
Authors: Lasala Ignacio , McKelvy Aubrey , Braun James , Paniagua Guillermo , Choquet Etienne , André Thierry , Falempin Francois
Published: August 2024

This manuscript evaluates the use of an actively cooled aerodynamic probe body with integrated optics to perform short focal length laser diagnostics within high-temperature, high-supersonic flows. A novel probe with a “ship’s bow” shape and an open cycle cooling scheme ending in a matrix of effusion holes is presented. The flow around the probe is studied numerically using 3D Steady Reynolds-Averaged Navier-Stokes (RANS) simulations at Mach 6, with free stream total conditions of 1700 K and 44.2 bar. The laser trajectory is calculated using the ray propagation equation to ensure that it deviates minimally while going through regions of gradients in refractive index. The location and shape of the detached shock formed ahead of the probe is extracted, and the minimum focal length achievable for measurement of the undisturbed flow-field is determined. The sensitivity of the bow shock shape to changes in cooling pressure between 1.33 and 1.835 bar, and to blocked holes has been computed. Finally, the flow through the effusion system of the probe is tested experimentally, ensuring its proper operation, and checking the consistency of the effusion boundary conditions used in the numerical study.
The Effect of FELTMETAL™ Porous Transport Layer Structure on Performance of Anion Exchange Membrane Water Electrolyzers
Authors: Motyka Elaine , Volpe Erin , Roeseler Stefan , Plessinger Ryan , Noyes Tyler , Li Chenyu , Park Habin , Kohl Paul , Mustain William , Kweder Jonathan
Published: August 2024

The porous transport layer (PTL), or gas diffusion layer (GDL), is a critical component in the performance of anion exchange membrane water electrolyzers (AEMELs) for hydrogen production and hydrogen supply. This work focuses on how the structure of FELTMETAL™ (FM) affects the critical functions of the oxygen evolution reaction (OER) electrode in an AEMEL. As a sintered-particle material with high levels of open pores, FM has high total porosity which positively affects mass transport of the gas and water from the PTL but increases the electrical resistivity and contact resistance. Due to the nature of the high-aspect ratio particles in FM, it also has high surface area which improves electrical properties and enables high current density during AEMEL operation. However, sintered materials typically have a trade-off between total porosity and pore size which can lead to mass transport issues if the pore size and distribution are too tight. Previous experimental electrolysis work determined that increasing the %-density of FM from 18%-density to 60%-density favorably increased current density at a given applied voltage, but it was likely that mass transport issues related to bubble formation and removal caused variation in performance and a decrease in current density over time. This work ultimately aimed to determine the effect of particle size on the structure of the FM PTL (pore size, total porosity, surface area) on AEMEL performance (current density, applied voltage, voltage stability over time, overpotentials). The study evaluated OER PTL FM with distinctly different %-densities and particle size distributions of Ni-alloy HastelloyX. The structures were characterized by metallography and bubble point testing. The AEMEL performance was characterized by polarization and electrochemical imprudence spectroscopy (EIS). Because the work focuses on the OER PTL structure, other key components of the experimental AEMEL were not varied, using standard commercial materials. It was found that the using a finer particle size distribution had a significant positive effect on polarization responses, specifically voltage at 1A/cm2, steady state voltage, and activation overpotential. The finer particle structure likely has increased total pore number and area-% open pores. It is possible that FM PTL materials comprised of finer fiber can enable performance improvement at a lower %-density, reducing the material required to make the PTL.
Multidisciplinary Design Optimization With Multiple Degrees of Freedom for an Axial Compressor Based on Data-Driven
Authors: Luo Chuwei , Chen Jiang , Liu Yi , Xiang Hang
Published: August 2024

Compressor design represents a multidisciplinary coupling problem encompassing aerodynamics, structure strength, vibration, fatigue, and acoustics. Multidisciplinary design optimization enables a comprehensive consideration of the interconnectedness among these disciplines, reasonably balances the conflicting requirements, and ultimately enhances the performance of products significantly while reducing the development cycle. In this paper, a multidisciplinary optimization system is established based on a data-driven multiobjective evolution algorithm. This algorithm is combined with the directly manipulated free-form deformation method to achieve multi-degree-of-freedom parameterized control. The research focuses on optimizing the aerodynamic and aeroelastic design of a 1.5-stage axial flow compressor in a gas turbine. Maximum efficiency and surge margin are set as the optimization objectives, while the constraint conditions involve flow rate, total pressure ratio, as well as the strength and resonance margin of the rotor blade. To improve the prediction accuracy of surge margin during optimization, a successive approximation method combined with efficiency-based residual convergence determination is utilized. The results show a significant reduction in the stress distribution of blades, with the maximum stress value decreased by 30.6%. Simultaneously, the surge margin of the compressor is increased by 3.36%, and the efficiency at the design point is also slightly improved. The optimization system can not only ensure optimization effectiveness, but also greatly reduce the design variables and evaluation time, which is effectively applicable to the multidisciplinary design optimization of compressors.
Windage Characteristics of a Compressor Stator Well Cavity
Authors: Erdem Erinc , Kahraman Ahmet Cuneyt , Garip Onur , Sal Sinan
Published: August 2024

This article aims at the investigation of a generic compressor stator well cavity flowfield of a high pressure compressor stage. Swirl ratio, static pressure distributions are thoroughly investigated together with windage power for three different engine thrust levels and three different clearance levels at high thrust cases. An experimental test case from Kong et. al [3]–[4] has been selected to validate the numerical method at five rotational speeds and two pressure ratios employing measured/predicted labyrinth seal clearances. One-dimensional cavity solver with three cavity approach is also employed to compare the results with experimental data. Contrary to a rotorstator cavity with radial inflow, stator well cavity flow displays a reduction in swirl ratio throughout the entire well and increase in windage power loss with higher λT, essentially with more flow. This is because well cavities are too shallow and located at high radii with low swirl leakage inflow, where torques dominate and dictate swirl distributions. Upstream cavity on the right hand side of the seal and labyrinth seal cavity are found to determine the windage power loss and associated temperature rise. The effect of downstream cavity located on the left hand side of the labyrinth seal is found to be less important.
Techno-Economic Analysis of the Solid Oxide Semi-Closed CO2 Cycle for Different Plant Sizes
Authors: Martinelli Matteo , Campanari Stefano , Martelli Emanuele
Published: August 2024

This work presents a detailed techno-economic evaluation of the SOS-CO2 cycle, a hybrid semi-closed cycle with solid oxide fuel cells developed by Politecnico di Milano. for different plant sizes, ranging from large utility plants (400 MWel) to industrial applications (50 MWel). The analysis includes the design and sizing of all the cycle components, including specific design optimization models for the most critical cycle components such as the regenerative heat exchanger and the turbine. Results are compared with the performance of the Allam cycle, an oxy-combustion cycle with higher technology readiness level. The results show that the SOS-CO2 cycle maintains high efficiency over the whole size range thanks to the modularity of the fuel cell and the regenerator which counterbalances the decrease in turbomachine efficiency at small sizes. For the utility scale plant, despite its higher specific investment cost (3761 €/kW vs. 2490€/kW), the SOS-CO2 cycle appears to be competitive with the Allam cycle in terms of cost of electricity (128.4 €/MWh and 127.8 €/MWh of the Allam cycle) thanks to its higher efficiency (68.9% vs. 53.1%). At smaller sizes, the higher efficiency and the lower dependance on the economies of scale make the SOS-CO2 more economically advantageous: for the 50 MWel plant, the cost of electricity of the SOS-CO2 is 175.8 €/MWh vs. 205.8 €/MWh of the Allam cycle.
The Purdue High-Speed Small Core Turbine Facility
Authors: Bhatnagar Lakshya , Castillo Sauca Antonio , Sanchez de la Rosa Diego , Paniagua Guillermo , Clemens Eugene , Bloxham Matthew
Published: August 2024

Short-duration facilities, with testing time on the order of milliseconds to seconds, offer cost-effective solutions to achieve engine-relevant pressure and temperature ratios. Short-duration facilities have high levels of heat loss that require careful accounting for efficiency calculation[1]. The Purdue Small Turbine Aerothermal Rotating Rig (STARR) was developed to test engine-representative hardware for small core turbine applications. The STARR facility is a two-stage rotating test turbine running at engine-representative Reynolds and Mach numbers capable of fast transients and steady operation for up to 6 hours with the enhanced pressure vessels in development. The facility is purpose-built to test advancements in critical technologies for clean aviation, pushing towards higher OPR engines, hybrid propulsion, and multi-stream engines. The facility is designed to be modular, allowing faster turnaround times for new test articles. This paper presents the design, control, and operation of the facility. Efficiency measurements in engine-representative test rigs are a challenging prospect due to the narrow uncertainty band required, ideally less than 0.5% uncertainty, to detect the incremental improvements achieved by turbine designers. For a small core turbine, accurately quantifying the tip clearance is also critical to assess relative changes in performance. To that end, the instrumentation used for efficiency measurement and resolving unsteady flow phenomenon is presented. The inlet characterization and commissioning of the test section are presented. Uncertainty is quantified on efficiency measurement through a comprehensive framework [2] that includes both precision and absolute level of uncertainty. The uncertainty is propagated from the individual sensor to the final efficiency calculation. The total uncertainty for mechanical efficiency presented is of the order of 0.55%. The challenges faced in the operation of such a facility are highlighted, along with the steps proposed to mitigate them.
Blowoff Characteristics of a Bluff-Body Stabilized, Multi-Element, Lean Premixed Pre-Vaporized Combustor for Supersonic Transport Applications
Authors: Passarelli Mitchell L. , Wonfor Samuel E. , Zheng Andy X. , Mazumdar Yi , Steinberg Adam M. , Bower Hannah , Hong John , Venkatesan Krishna
Published: August 2024

This work explores the flame stabilization and blowoff characteristics of a novel lean premixed pre-vaporized (LPP) combustor design for potential commercial supersonic transport (CST) applications. CST operating conditions involve higher combustor inlet temperatures and lower inlet pressures than encountered in conventional subsonic aeroengines. Additionally, the LPP combustor investigated in this work is a multi-element subsonic flow design, with four bluff-body stabilized, annular “main” flames surrounding a central, swirl-stabilized pilot flame. Existing blowoff studies have not explored the combined effects of multi-element flames with varying temperature and pressure simultaneously. This work presents experimental analysis of the conditions that lead to blowoff in such a combustor. The experimental data consists of simultaneous pressure fluctuations, high-speed OH* chemiluminescence imaging and low-speed kerosene planar laser induced fluorescence imaging. The operating conditions for each data set were used to evaluate the Reynolds number (Re) and Damköhler number (Da). Plots of Da versus Re indicate that the Da at blowoff is lower than that reported in literature for flames stabilized on axisymmetric bluff bodies. It is hypothesized that the observed trend is due, in part, to the presence of the central pilot flame which breaks the axisymmetry of the individual main flames and acts as an ignition source for low Da conditions. An investigation of a case with intermittent blowoff reveals the presence and effects of unforeseen hysteresis in the combustor.
Semi-Closed Oxy-Combustion Combined Cycles (SCOC-CC) for Combined Heat and Power Applications
Authors: Zelaschi Andrea , Giostri Andrea , Chiesa Paolo , Martelli Emanuele
Published: August 2024

This study focuses on the design and comparison of three utility-scale combined heat and power (CHP) cycles with carbon capture and storage (CCS): (i) a CHP semi-closed oxy-combustion combined cycle (SCOC-CC), (ii) a CHP natural gas combined cycle (NGCC) with post-combustion CCS, and (iii) a CHP NGCC with post-combustion CCS and supplementary firing. Performance evaluations are conducted at the design point and partial load (gas turbine at 30%) for different exports of high-temperature pressurized steam. The comparison is extended against two reference separate production systems with CCS, one based on post-combustion technologies, and another based on oxy-combustion. Simulations of the H-class gas turbines are performed using GS, a specific in-house validated software, while the heat recovery steam cycle is modelled using Thermoflex. The CO2 capture processes employ validated models in Aspen Plus. The results highlight the suitability of the SCOC-CC for CHP applications, demonstrating superior performance and flexibility compared to CHP post-combustion technologies at both nominal and minimum loads. The SCOC cycle achieves a maximum first-law efficiency of 65.95%, outperforming CCS technologies that generate electricity and heat separately and enabling fuel savings up to 9.2%.
Dynamic Response of a Rotor Supported on Hybrid Bearings in Air, Water, and Liquid Nitrogen: Measurements and Comparisons to Predictions
Authors: Yi Howon , Kim Kyuman , Jung Hyunsung , Ryu Keun
Published: August 2024

Modern liquid rocket engine turbopumps implement hybrid bearings, which combine hydrostatic and hydrodynamic fluid film principles, in compact and lightweight units known for their superior reusability, durability, and reliability. This study aims to provide extensive and reliable test data for the purpose of anchoring and benchmarking predictive tools for these bearings. This paper provides comprehensive dynamic response measurements of a rotor weighing 10.40 kg and approximately 60 mm in diameter at the bearing locations. The test rotor is supported on two hybrid journal bearings with a bearing length to bearing diameter ratio of approximately 0.42 and a bearing radial clearance to rotor radius ratio of around 0.0017. The bearings are tested with air, water, and liquid nitrogen, serving as surrogate test fluids for common propellants in liquid rocket engines. Rotor run-up and speed coast-down tests are conducted to measure shaft motion responses. The results clearly demonstrate that the rotordynamic characteristics of the test rotor supported on the hybrid journal bearings largely rely on properties of the test fluids and their feeding conditions. Notably, when air is pressurized into the test bearings, the shaft motion responses differ markedly from those observed with water and liquid nitrogen, primarily due to significantly lower stiffness and damping coefficients. Furthermore, rotor speed coast-down tests for each test fluid exhibit notable differences in coast-down speed over time characteristics, depending on the test fluid properties. The predicted rotor imbalance responses exhibit excellent correlation with the measurement data. The steady increase of demand and growth of the fluid film bearing technology for reusable rocket engines require accurate bearing design tools, the extensive component testing, and the implementation of the technology. The validated and developed bearing predictive models from previous research demonstrate well the characteristics of bearings under various operating fluids conditions. The findings and database presented in this work contribute not only to comprehending the performance of hybrid bearings but also to understanding and enhancing the dynamic characteristics of rotor systems supported by hybrid bearings.
The Effect of Mixture Variation and Initial Temperature on the NH2* Thickness of Spherically Propagating Laminar Ammonia Flames
Authors: Almarzooq Yousef M. , Hay Matthew , Mathieu Olivier , Kulatilaka Waruna D. , Petersen Eric L.
Published: August 2024

Interest in ammonia (NH3) in combustion has increased in recent years as a carbon-free fuel alternative. Therefore, understanding its combustion characteristics is crucial. One way to increase the knowledge of ammonia combustion is by investigating the flame zone of a laminar flame. Using a high-spatial-resolution flame zone measurement technique developed by the current research group, the flame zone of different NH3-containing mixtures was measured experimentally. Those measurements were achieved by investigating spherically propagating flames using a chemiluminescence imaging diagnostic with the focus on NH2* profiles. The effect of the fuel mixture on the profile shape was investigated by examining two different mixtures. The first was an oxy-ammonia mixture consisting of NH3 + oxygen-enriched oxidizer where the oxygen (O2) concentration was varied from 25% to 40%. The second was a blend of NH3-H2 where the NH3 concentration (XNH3) was varied from 0.5 to 0.8. Additionally, the effect of the initial temperature was investigated by varying it from 293 to 373 K for three different mixtures, namely NH3 + (35% O2 + 65% N2), (0.7 NH3 + 0.3 H2) / air, and (0.45 H2 + 0.4 NH3 + 0.15 N2) / air. In all investigated mixtures, the initial pressure was fixed at 1 atm and the equivalence ratio was fixed at Φ = 1.0. The study revealed that increasing the O2 concentration in the oxy-ammonia mixture produced thinner flames. On the contrary, increasing the XNH3 in the NH3-H2 blend produced slightly thicker flames. Varying the initial temperature has two different responses for the three designated mixtures. In the oxy-ammonia mixture and the NH3-H2 blend, increasing the initial temperature resulted in the flame being thinner. On the other hand, increasing the initial temperature produced a slightly thicker flame for the H2-NH3-N2 blend. The predicted NH2* profile thicknesses from chemical kinetics agree with the measurements except for the H2-NH3-N2 blend, where the kinetics model underpredicted the thickness by a significant difference.
sCO2 Cycle Selection for Waste Heat Recovery From Aircraft Engine
Authors: Vesely Ladislav , Andress William , Paniagua Guillermo , Otto Marcel , Kapat Jayanta , Bury Claire-Phonie
Published: August 2024

The reduction of emissions for any sector, such as aviation, can be done via alternative fuels (i.e., direct approach) and/or utilization of waste heat (i.e., indirect approach). With an indirect approach, waste heat recovery (WHR) systems can provide onboard electrical power and eliminate or reduce the need to produce electrical power with other systems. An engine with a WHR system could potentially produce similar power/thrust with less fuel consumption. WHR systems could have additional benefits for the engine core and bypass flow. This work is focused on the sCO2 power cycle selection for a potential WHR system for an aircraft engine based on a Leap-1B engine using H2 as the working fuel and NH3 as a fuel carrier. Several sCO2 power cycle layouts are investigated for each case, including simple, recuperative, re-compression, precompression, and split expansion. Optimization of the selected cycle layout for the maximum power requirement and heat availability to transfer to the NH3 line or bypass is performed. The results show potential benefits and disadvantages of each cycle layout and demonstrate that the WHR system can meet the 180-kW power generation requirement for the airplane and still provide significant heat to the NH3 line or bypass flow.
An Investigation of a Multi-Injector, Premix/Micromix Burner Burning Pure Methane to Pure Hydrogen
Authors: Durocher Antoine , Fan Luming , Füri Marc , Bourque Gilles , Sirois Julien , May David , Bergthorson Jeffrey M. , Yun Sean , Vena Patrizio
Published: August 2024

Micromix combustion technology has been identified as a promising strategy to mitigate the risks associated with burning high-hydrogen-content fuels. This technology has recently been introduced in premixed injector designs to develop burners with broader fuel flexibility, allowing the combustion of fuels ranging from natural gas, or currently available hydrocarbons, to pure hydrogen by controlling the micromix fuel ratio (MFR). Modifying this additional operating parameter can lead to premixed, partially-premixed, and micromixed combustion, each having different stability mechanisms. The combustion characteristics of such flames in an industrial combustion environment with hundreds of injectors is unknown. A multi-injector configuration, consisting of five (5) injectors placed in a cross pattern, is used to investigate the combustion of pure methane to pure hydrogen, and different blends. Stability and combustion dynamic maps are first obtained at atmospheric temperature and pressure for fuel-lean mixtures of H2/CH4 ranging from 0/100, 70/30, 90/10, to 100/0%, by volume. For each fuel mixture, the equivalence ratio is adjusted to maintain the same adiabatic flame temperature throughout the experiments. An increase in blowoff limit is observed for the multi-injector array compared to a single nozzle, while flashback occurs more rapidly for dominantly-premixed conditions with high-hydrogen-content fuel. In addition to extending the flashback limit, micromixed flames are generally quieter for high-hydrogen-content fuels. Laser diagnostics are performed on selected operating conditions with hydrogen content of 0, 30, 50, 70, 90, and 100%. Eight cases are investigated in this work at a constant bulk inlet velocity to highlight the impact of hydrogen content and MFR on the flame shape. Two-dimensional (2D) PIV, OH and acetone planar laser-induced fluorescence (PLIF), as well as acoustic measurements, are performed simultaneously. The planar measurements show that the OH-PLIF signal becomes thinner and non-axisymmetric as MFR is increased from 0 to 100%, with the flames gradually transitioning from V-shaped to M-shaped, before stabilizing as jet flames in crossflow.
Modeling of Metal Matrix Concentrated Solar Receivers for sCO2 Power Blocks
Authors: Duggirala Vyas , Hegde Venkatanarasimha , Reddy Venkateswara , Kumar Pramod
Published: August 2024

Supercritical CO2 power blocks for Concentrating Solar Power (CSP) with novel metal matrix solar receivers have the potential to reduce operating expenses while improving overall system efficiencies. These concentrated solar receivers integrated with a metal matrix-based phase change (PCM) thermal storage medium provide the compounding effect of an efficient heat exchanger while also integrating thermal storage within the receiver. Detailed numerical modeling of such devices with enthalpy-porosity-based formulation for phase change and turbulent convective heat transfer for the sCO2 microchannels is described in the current work. With sCO2 power blocks operating at temperatures and pressures beyond 800°C and 200 bar, different high-temperature PCMs are studied. A detailed steady charging followed by discharge and charging transients is simulated to analyze the thermal performance of these devices. In the current work, the energy storage density of PCMs is studied, followed by an analysis of the movement of the melt-pool interface over the streamwise length of a high corrugation wavy microchannel. A scaling analysis is carried out to estimate the heat transfer coefficients while compare them with the numerical model predictions. The results from the current work can be utilized for sizing and detailed design of integrated solar receivers for high-temperature sCO2 power block applications.
Impingement Flow and Heat Transfer With Fractal Grids
Authors: Tang Chen , Acharya Sumanta
Published: August 2024

Jet impingement heat transfer is widely acknowledged as an effective approach for localized cooling applications. A new passive method to augment jet-impingement heat transfer based on inserting a fractal-grid (FG) at the jet-nozzle exit is explored in this paper. Both the flow behavior and heat transfer characteristics are investigated experimentally for two fractal grids (FG1 and FG2) placed immediately downstream of the jet-array and with different jet-to-target plate spacings (H/D). Results are compared with those using a standard grid with round-holes (RG) and same blockage ratio. The results indicate that the FG2 provides significant heat transfer enhancements for the smaller H/D values. An enhancement of 57% and 34% is obtained respectively for spanwise-averaged and spatially-averaged Nusselt number for FG2 case at H/D = 2 compared to the baseline no-grid case. The flow measurements indicate that the turbulence intensity and spectral characteristics downstream of the FG are different than those of the baseline and RG cases and are the primary drivers for the heat transfer enhancements. These differences generally reduce with increasing distances of the target surface from the jet-nozzle indicating that highest heat transfer enhancements are achieved for the lowest H/Ds. This is confirmed by the Nusselt number results.
Laser Powder Bed Fusion Manufactured Hydrostatic Journal Bearings for Turbomachinery: Design and Measurements of Static Load Testing With Air, Water, and Liquid Nitrogen
Authors: Baek Chaeyeon , Jung Hyunsung , Heo Junwon , Kim Kyuman , Ryu Keun
Published: August 2024

Modern turbomachinery demands simplified components and compact shaft support systems. This study introduces novel hydrostatic journal bearings incorporating multiple tilting pads and fluid feeding features, which are manufactured with Direct Metal Laser Melting (DMLM) technology, an advanced laser powder bed fusion manufacturing process. Two test bearings, fabricated by fusing extremely thin layers of Inconel 718 powder, incorporate fluid external feed pressurization features without the need for recesses. One test bearing features unique internal feeding hole configurations, which combine multiple holes with an angled injection feature, while the other test bearing includes distinctive porous layers on the bearing pad surfaces. This paper provides a comprehensive overview of the design, fabrication process, and static load characteristic measurements of these innovative bearings. A simple static load test rig is used to measure the flow rate, temperature, and stiffnesses of the test bearings while supplying compressed air, water, and liquid nitrogen with increasing static loads. The performance of these bearings is compared with counterparts produced via conventional subtractive manufacturing (CNC machining). In general, the bearings lubricated with liquid nitrogen exhibit a higher load capacity compared to those lubricated with air. This study confirms the static load performance of metal 3D printed hydrostatic journal bearings, marking a significant advancement in the application of additive manufacturing for turbomachinery bearings. The findings offer valuable insights into the potential of additive manufacturing in producing bearings for extreme operating conditions and various lubricants.
A Comparison of Flat and Hierarchical Structures in Aircraft Engine Fault Classification Algorithms
Authors: Loboda Igor , Pérez-Ruiz Juan Luis , González Castillo Iván , Yepifanov Sergiy
Published: August 2024

Gas turbine engine diagnostic algorithms using gas path measurements present an important component of an engine monitoring system. Pattern recognition and machine learning techniques are increasingly involved in gas turbine performance diagnostics. The necessary fault classifications are formed following the principles of either flat or hierarchical structures. With the flat classification composed of all elementary fault classes, a classifier makes its decision at once. In contrast, the hierarchical classification implies grouping elementary classes into “mega-classes”, and the classification process propagates successively through different levels down to the lowest level of the elementary classes. Most gas turbine diagnostic algorithms use the flat classification structure. However, recent studies indicate that the hierarchical classification principle has some advantages, although these studies and our preliminary calculations show that the difference between these two principles can be small.

Comparing two algorithms, flat classification-based and hierarchical classifications-based, the present study aims to ascertain which of the classifications is more accurate and why. This will allow us to provide a monitoring system designer with clear guidance on the fault classification process. Both algorithms include the same steps: a) feature extraction (computing measurement deviations), b) fault classification construction as a set of numerous deviation vectors (patterns) induced by different engine faults, c) learning of artificial neural networks on the fault classification data (learning set), and d) verification of the networks on similar data called a validation set. The comparison criteria are based on a confusion matrix that unites the probabilities of correct and wrong fault recognition. For an accurate analysis, the compared diagnostic algorithms differ from each other only by a classification structure. The other algorithms’ elements and input learning and validation sets are the same.

For generating the necessary measurement data, this study uses ProDiMES as a benchmarking platform designated for comparing diagnostic solutions. This platform provides a realistic simulation of a fleet of healthy and faulty aircraft engines using their nonlinear thermodynamic model.

The comparison results show that the algorithm with the hierarchical classification structure differs in the diagnosis of particular fault conditions, but in general, for all conditions it does not have advantages against the flat classification algorithm.
Cancer-associated DNA hypermethylation of Polycomb targets requires DNMT3A dual recognition of histone H2AK119 ubiquitination and the nucleosome acidic patch
Authors: Gretarsson Kristjan H. , Abini-Agbomson Stephen , Gloor Susan L. , Weinberg Daniel N. , McCuiston Jamie L. , Kumary Vishnu Udayakumar Sunitha , Hickman Allison R. , Sahu Varun , Lee Rachel , Xu Xinjing , Lipieta Natalie , Flashner Samuel , Adeleke Oluwatobi A. , Popova Irina K. , Taylor Hailey F. , Noll Kelsey , Windham Carolina Lin , Maryanski Danielle N. , Venters Bryan J. , Nakagawa Hiroshi , Keogh Michael-Christopher , Armache Karim-Jean , Lu Chao
Published: August 2024

During tumor development, promoter CpG islands that are normally silenced by Polycomb repressive complexes (PRCs) become DNA-hypermethylated. The molecular mechanism by which de novo DNA methyltransferase(s) [DNMT(s)] catalyze CpG methylation at PRC-regulated regions remains unclear. Here, we report a cryo–electron microscopy structure of the DNMT3A long isoform (DNMT3A1) amino-terminal region in complex with a nucleosome carrying PRC1-mediated histone H2A lysine-119 monoubiquitination (H2AK119Ub). We identify regions within the DNMT3A1 amino terminus that bind H2AK119Ub and the nucleosome acidic patch. This bidentate interaction is required for effective DNMT3A1 engagement with H2AK119Ub-modified chromatin in cells. Further, aberrant redistribution of DNMT3A1 to Polycomb target genes recapitulates the cancer-associated DNA hypermethylation signature and inhibits their transcriptional activation during cell differentiation. This effect is rescued by disruption of the DNMT3A1–acidic patch interaction. Together, our analyses reveal a binding interface critical for mediating promoter CpG island DNA hypermethylation, a major molecular hallmark of cancer.
Paley–Wiener-type theorems for the canonical Fourier–Bessel transform
Authors: Fei Minggang , Si Yuanyuan
Published: August 2024

The aim of this paper is to establish several versions of Paley–Wiener-type theorems for the canonical Fourier–Bessel transform, which is a Bessel type of linear canonical transform indexed by a matrix parameter m [Formula: see text].
Cobotics: The Evolving Roles and Prospects of Next‐Generation Collaborative Robots in Industry 5.0
Authors: Rahman Md. Mijanur , Khatun Fatema , Jahan Ismat , Devnath Ramprosad , Bhuiyan Md. Al-Amin
Published: August 2024

The emergence of Industry 5.0 marks a transformative era in manufacturing industry that is driven by the integration of advanced technologies. It is a renewed focus on human–robot collaboration. At the forefront of this industrial revolution stands Cobotics, a field that emphasizes the cooperative interaction between humans and robots in shared workspaces. This research paper delves into the critical role and implications of Cobotics in the context of Industry 5.0. The study addresses the research problem of effectively integrating Cobots into industrial processes, considering technical, economic, and social challenges. The paper’s objectives include surveying existing literature, analyzing developments and trends, showcasing real‐world examples, and proposing future research directions. A comprehensive literature review explores Cobotics’ foundations and its alignment with Industry 5.0 principles. The research presents real‐world examples of successful Cobot integration across various industries, demonstrating benefits such as increased productivity, improved quality, and enhanced worker safety. The paper identifies gaps in existing knowledge and contributions to the field, emphasizing the need for research in simplified programming, cost–benefit analysis, and ethical frameworks. This research paper illuminates the central role of Cobotics in Industry 5.0, where human–robot collaboration, innovation, and inclusivity are paramount. It anticipates a future where Cobotics will continue to evolve, shaping industries, empowering the workforce, and driving sustainable, data‐driven industrial transformations.
Modulation of High‐Frequency rTMS on Reward Circuitry in Individuals with Nicotine Dependence: A Preliminary fMRI Study
Authors: Wang Tao , Li Ruiyang , Chen Dongyan , Xie Mei , Li Zhiqiang , Mao Huan , Ling Yuting , Liang Xiaoyun , Xu Guojun , Zhang Jianjun
Published: August 2024

Although previous studies have shown that repetitive transcranial magnetic stimulation (rTMS) can ameliorate addictive behaviors and cravings, the underlying neural mechanisms remain unclear. This study aimed to investigate the effect of high‐frequency rTMS with the left dorsolateral prefrontal cortex (L‐DLPFC) as a target region on smoking addiction in nicotine‐dependent individuals by detecting the change of spontaneous brain activity in the reward circuitry. We recruited 17 nicotine‐dependence participants, who completed 10 sessions of 10 Hz rTMS over a 2‐week period and underwent evaluation of several dependence‐related scales, and resting‐state fMRI scan before and after the treatment. Functional connectivity (FC) analysis was conducted with reward‐related brain regions as seeds, including ventral tegmental area, bilateral nucleus accumbens (NAc), bilateral DLPFC, and bilateral amygdala. We found that, after the treatment, individuals showed reduced nicotine dependence, alleviated tobacco withdrawal symptoms, and diminished smoking cravings. The right NAc showed increased FC with right fusiform gyrus, inferior temporal gyrus (ITG), calcarine fissure and surrounding cortex, superior occipital gyrus (SOG), lingual gyrus, and bilateral cuneus. No significant FC changes were observed in other seed regions. Moreover, the changes in FC between the right NAc and the right ITG as well as SOG before and after rTMS were negatively correlated with changes in smoking scale scores. Our findings suggest that high‐frequency L‐DLPFC‐rTMS reduces nicotine dependence and improves tobacco withdrawal symptoms, and the dysfunctional connectivity in reward circuitry may be the underlying neural mechanism for nicotine addiction and its therapeutic target.