bluuebunny/crossref_metadata_2025 huggingface dataset:
QTL mapping and candidate gene analysis of low‐temperature tolerance at the germination stage of soybean
Authors: Zheng Liping , Xie Jianguo , Sun Xingmiao , Zheng Yuhong , Meng Fanfan , Fan Xuhong , Li Guang , Zhang Yunfeng , Wang Mingliang , Zhou Ruo , Qiu Hongmei , Wang Shuming , Jiang Hongwei
Published: September 2023

When soybean seeds encounter low temperature during germination, the vigour and germination of soybean seeds are affected, which leads to a lack of seedlings and weak seedlings, resulting in yield reduction. In‐depth analysis of the genetic mechanism of soybean seed germination tolerance to low‐temperature stress and the cultivation of soybean‐tolerant varieties is the key to resisting low‐temperature stress at the germination stage. In the present study, a chromosome segment substitution line (CSSL) population constructed by wild soybean ZYD00006 and cultivated soybean SN14 was used to map three quantitative trait loci (QTLs). Five candidate genes were obtained by gene annotation, GO enrichment analysis and protein function prediction. The candidate genes were subjected to bioinformatics analysis, qRT‐PCR analysis, trypsin activity analysis and soluble protein content analysis. The results showed that the secondary and tertiary structures of the Glyma.09G162700 proteins were mutated. Within 0–72 h, the expression of Glyma.09G162700 in the two materials with different tolerances was consistent, and the change in trypsin activity was consistent with the change in protein expression. Through haplotype analysis, Glyma.09G162700 produced two haplotypes at −2420 bp. The germination rate (GR) and relative germination rate (RGR) of the two haplotypes were significantly different, indicating that the two haplotypes have wide applicability in soybean resources. In summary, Glyma.09G162700 may be a candidate gene for low‐temperature tolerance at the germination stage of soybean. These results provide an important theoretical basis and marker information for analysing the mechanism of low‐temperature tolerance in soybean germination stage and cultivating low‐temperature‐tolerant varieties.
Loss ratio dynamics
Authors: Grace Martin F.
Published: September 2023

Many studies of the insurance profit cycle use industry‐level annual data and focus on the existence of an AR(2) process. We take a different approach by adopting the idea of possible hard and soft markets, but they are not necessarily cyclical in the classic sense. In addition to aggregated data, we use quarterly firm‐level data to examine loss ratio behavior over time. This approach allows one to assess the firm‐level heterogeneity in the insurance market. We further use a Markov switching model to assess the heterogeneity of response to economic variables. Using a K‐means cluster approach, we examine the different clusters of firms and their different behavior over 2001q1−2020q4.
Physical activity, residential greenness, and cardiac autonomic function
Authors: Korpisaari Maija , Puhakka Soile , Farrahi Vahid , Niemelä Maisa , Tulppo Mikko P. , Ikäheimo Tiina , Korpelainen Raija , Lankila Tiina
Published: September 2023

Purpose

This population‐based study examines the associations between physical activity (PA), residential environmental greenness, and cardiac health measured by resting short‐term heart rate variability (HRV).

Methods

Residential greenness of a birth cohort sample (n = 5433) at 46 years was measured with normalized difference vegetation index (NDVI) by fixing a 1 km buffer around each participant's home. Daily light PA (LPA), moderate PA (MPA), vigorous PA (VPA), and the combination of both (MVPA) were measured using a wrist‐worn accelerometer for 14 days. Resting HRV was measured with a heart rate monitor, and generalized additive modeling (GAM) was used to examine the association between PA, NDVI, and resting HRV.

Results

In nongreen areas, men had less PA at all intensity levels compared to men in green areas. Women had more LPA and total PA and less MPA, MVPA, and VPA in green residential areas compared to nongreen areas. In green residential areas, men had more MPA, MVPA, and VPA than women, whereas women had more LPA than men. GAM showed positive linear associations between LPA, MVPA and HRV in all models.

Conclusions

Higher LPA and MVPA were significantly associated with increased HRV, irrespective of residential greenness. Greenness was positively associated with PA at all intensity levels in men, whereas in women, a positive association was found for LPA and total PA. A positive relationship of PA with resting HRV and greenness with PA was found. Residential greenness for promoting PA and heart health in adults should be considered in city planning.
Generation of skin tone and pigmented region‐modified images using a pigment discrimination model trained with an optical approach
Authors: Jung Geunho , Kim Semin , Lee Jongha , Yoo Sangwook
Published: September 2023

Background

Skin tone and pigmented regions, associated with melanin and hemoglobin, are critical indicators of skin condition. While most prior research focuses on pigment analysis, the capability to simulate diverse pigmentation conditions could greatly broaden the range of applications. However, current methodologies have limitations in terms of numerical control and versatility.

Methods

We introduce a hybrid technique that integrates optical methods with deep learning to produce skin tone and pigmented region‐modified images with numerical control. The pigment discrimination model produces melanin, hemoglobin, and shading maps from skin images. The outputs are reconstructed into skin images using a forward problem‐solving approach, with model training aimed at minimizing the discrepancy between the reconstructed and input images. By adjusting the melanin and hemoglobin maps, we create pigment‐modified images, allowing precise control over changes in melanin and hemoglobin levels. Changes in pigmentation are quantified using the individual typology angle (ITA) for skin tone and melanin and erythema indices for pigmented regions, validating the intended modifications.

Results

The pigment discrimination model achieved correlation coefficients with clinical equipment of 0.915 for melanin and 0.931 for hemoglobin. The alterations in the melanin and hemoglobin maps exhibit a proportional correlation with the ITA and pigment indices in both quantitative and qualitative assessments. Additionally, regions overlaying melanin and hemoglobin are demonstrated to verify independent adjustments.

Conclusion

The proposed method offers an approach to generate modified images of skin tone and pigmented regions. Potential applications include visualizing alterations for clinical assessments, simulating the effects of skincare products, and generating datasets for deep learning.
Does spouse's parental housing support affect one's happiness: Evidence from China
Authors: Li Zhongwu , Lu Fengzhi
Published: September 2023

Objective

The study empirically investigates the relationship between spouse's parental housing support and one's happiness.

Methods

Leveraging three waves of data from the Chinese General Social Survey, this study employs a methodological approach that encompasses the utilization of an ordinal logit model, ordinary least squares regression, selection on observables to measure selection on unobservables, and Lewbel's instrumental variable method.

Results

We find that spouse's parental housing support has an asymmetric association with one's happiness within family: wife's parental housing support is not associated with her husband's happiness, while husband's parental housing support is positively associated with his wife's happiness. This positive association is notably pronounced among women from rural backgrounds and younger women residing in urban areas.

Conclusion

Our findings contradict the assertion that women have achieved economic and psychological independence from men and men's families. It elucidates that women continue to rely on the conventional patriarchal system for enhanced welfare. Specifically, women, particularly those residing in rural areas, and younger urban cohorts continue to anticipate their spouses' parental housing support in contemporary China.
COVID‐19 after hematopoietic cell transplantation and chimeric antigen receptor (CAR)‐T‐cell therapy
Authors: Kampouri Eleftheria , Hill Joshua A. , Dioverti Veronica
Published: September 2023

More than 3 years have passed since Coronavirus disease 2019 (COVID‐19) was declared a global pandemic, yet COVID‐19 still severely impacts immunocompromised individuals including those treated with hematopoietic cell transplantation (HCT) and chimeric antigen receptor‐T‐cell therapies who remain at high risk for severe COVID‐19 and mortality. Despite vaccination efforts, these patients have inadequate responses due to immunosuppression, which underscores the need for additional preventive approaches. The optimal timing, schedule of vaccination, and immunological correlates for protective immunity remain unknown. Antiviral therapies used early during disease can reduce mortality and severity due to COVID‐19. The combination or sequential use of antivirals could be beneficial to control replication and prevent the development of treatment‐related mutations in protracted COVID‐19. Despite conflicting data, COVID‐19 convalescent plasma remains an option in immunocompromised patients with mild‐to‐moderate disease to prevent progression. Protracted COVID‐19 has been increasingly recognized among these patients and has been implicated in intra‐host emergence of SARS‐CoV‐2 variants. Finally, novel SARS‐CoV2‐specific T‐cells and natural killer cell‐boosting (or ‐containing) products may be active against multiple variants and are promising therapies in immunocompromised patients.
Expression of human thrombomodulin by GalTKO.hCD46 pigs modulates coagulation cascade activation by endothelial cells and during ex vivo lung perfusion with human blood
Authors: Burdorf Lars , Gao Zhuo , Riner Andrea , Sievert Evelyn , Harris Donald G. , Kuravi Kasinath V. , Morrill Benson H. , Habibabady Zahra , Rybak Elana , Dahi Siamak , Zhang Tianshu , Schwartz Evan , Kang Elizabeth , Cheng Xiangfei , Esmon Charles T. , Phelps Carol J. , Ayares David L. , III Richard N. Pierson , Azimzadeh Agnes M.
Published: September 2023

Thrombomodulin is important for the production of activated protein C (APC), a molecule with significant regulatory roles in coagulation and inflammation. To address known molecular incompatibilities between pig thrombomodulin and human thrombin that affect the conversion of protein C into APC, GalTKO.hCD46 pigs have been genetically modified to express human thrombomodulin (hTBM). The aim of this study was to evaluate the impact of transgenic hTBM expression on the coagulation dysregulation that is observed in association with lung xenograft injury in an established lung perfusion model, with and without additional blockade of nonphysiologic interactions between pig vWF and human GPIb axis. Expression of hTBM was variable between pigs at the transcriptional and protein level. hTBM increased the activation of human protein C and inhibited thrombosis in an in vitro flow perfusion assay, confirming that the expressed protein was functional. Decreased platelet activation was observed during ex vivo perfusion of GalTKO.hCD46 lungs expressing hTBM and, in conjunction with transgenic hTBM, blockade of the platelet GPIb receptor further inhibited platelets and increased survival time. Altogether, our data indicate that expression of transgenic hTBM partially addresses coagulation pathway dysregulation associated with pig lung xenograft injury and, in combination with vWF‐GP1b‐directed strategies, is a promising approach to improve the outcomes of lung xenotransplantation.
Sensor-Based Planning and Control for Conformal Deposition on a Deformable Surface Using an Articulated Industrial Robot
Authors: Yang Yang , Cai Ying , Jung Yoon Yeo , Zhao Hangbo , Gupta Satyandra K.
Published: September 2023

Robotic manipulators can be used to deposit materials on non-planar surfaces. Conventional sensor-based industrial robots can only work on stationary surfaces, relying on the scanned data prior to printing. As a result, performing depositions that involve changes in plane motion presents significant challenges. The deposition of conformal materials on a time-varying deformable surface requires the manipulators to update coordinates in real time on the plane for positioning and orientation. This can be achieved by employing multiple sensors for manipulator motion planning and control, in order to prevent collisions between the tool and the surface. In this paper, we propose simple tool center point calibration, initial point coordinate estimation, and a gap compensation scheme to combine real-time feedback control and direct conformal deposition. Combining these elements allows us to maintain a controlled gap between the tooltip and the deformable surface during the deposition. We test the efficacy of the proposed approach by printing a single layer of ink patterns with approximately 950 μm line width on a deformable surface. We also characterize the printing quality with different gaps and printing steps and show that sensor-based control is critical in smooth printing. Finally, the effects of changing the relative position of the tooltip, different surface colors, and laser sensor position are characterized.
Automated Evaluation and Rating of Product Repairability Using Artificial Intelligence-Based Approaches
Authors: Liao Hao-Yu , Esmaeilian Behzad , Behdad Sara
Published: September 2023

Despite the importance of product repairability, current methods for assessing and grading repairability are limited, which hampers the efforts of designers, remanufacturers, original equipment manufacturers (OEMs), and repair shops. To improve the efficiency of assessing product repairability, this study introduces two artificial intelligence (AI) based approaches. The first approach is a supervised learning framework that utilizes object detection on product teardown images to measure repairability. Transfer learning is employed with machine learning architectures such as ConvNeXt, GoogLeNet, ResNet50, and VGG16 to evaluate repairability scores. The second approach is an unsupervised learning framework that combines feature extraction and cluster learning to identify product design features and group devices with similar designs. It utilizes an oriented FAST and rotated BRIEF feature extractor (ORB) along with k-means clustering to extract features from teardown images and categorize products with similar designs. To demonstrate the application of these assessment approaches, smartphones are used as a case study. The results highlight the potential of artificial intelligence in developing an automated system for assessing and rating product repairability.
Assessing the Manufacturability of Students’ Early-Stage Designs Based on Previous Experience With Traditional Manufacturing and Additive Manufacturing
Authors: Pearl Seth , Meisel Nicholas A.
Published: September 2023

As additive manufacturing (AM) usage increases, designers who wish to maximize AM’s potential must reconsider the traditional manufacturing (TM) axioms they may be more familiar with. While research has previously investigated the potential influences that can affect the designs produced in concept generation, little research has been done explicitly targeting the manufacturability of early-stage concepts and how previous experience and the presenting of priming content in manufacturing affect these concepts. The research in this paper addresses this gap in knowledge, specifically targeting differences in concept generation due to designer experience and presenting design for traditional manufacturing (DFTM) and design for additive manufacturing (DFAM) axioms. To understand how designers approach design creation early in the design process and investigate potential influential factors, participants in this study were asked to complete a design challenge centered on concept generation. Before this design challenge, a randomized subset of these participants received priming content on DFTM and DFAM considerations. These participants’ final designs were evaluated for both traditional manufacturability and additive manufacturability and compared against the final designs produced by participants who did not receive the priming content. Results show that students with low manufacturing experience levels create designs that are more naturally suited for TM. Additionally, as designers’ manufacturing experience levels increase, there is an increase in the number of designs more naturally suited for AM. This correlates with a higher self-reported use of DFAM axioms in the evaluation of these designs. These results suggest that students with high manufacturing experience levels rely on their previous experience when it comes to creating a design for either manufacturing process. Lastly, while the manufacturing priming content significantly influenced the traditional manufacturability of the designs, the priming content did not increase the number of self-reported design for manufacturing (DFM) axioms in the designs.
Development and Dynamic State Estimation for Robotic Knee–Ankle Orthosis With Shape Memory Alloy Actuators
Authors: Sun Zhi , Li Yuan , Zi Bin , Chen Bing
Published: September 2023

The development of rehabilitation robots has long been an issue of increasing interest in a wide range of fields. An important aspect of the ongoing research field is applying flexible components to rehabilitation equipment to enhance human−machine interaction. Another major challenge is to accurately estimate the individual’s intention to achieve safe operation and efficient training. In this article, a robotic knee−ankle orthosis (KAO) with shape memory alloy (SMA) actuators is developed, and the estimation method is proposed to determine the joint torque. First, based on the analysis of human lower limb structure and walking patterns, the mechanical design of the KAO that can achieve various rehabilitation training modes is detailed. Next, the dynamic model of the hybrid-driven KAO is established using the thermodynamic constitutive equation and Lagrange formalism. In addition, the joint torque estimation is realized by the nonlinear Kalman filter method. Finally, the prototype and human subject experiments are conducted, and the experimental results demonstrate that the KAO can assist lower limb movements. In the three experimental scenarios, reductions of 59.1%, 16.5%, and 73% of the torque estimation error during the knee joint movement are observed, respectively.
An Experimental Investigation of Sweeping Air/Mist Jet Film Cooling Through a Row of Passive Fluidic Oscillators
Authors: Abdelmaksoud Ramy , Wang Ting
Published: September 2023

Sweeping jet fluidic oscillators can be a promising candidate in film cooling applications since they have a large lateral jet spreading with more uniform cooling which can be considered an advantage when compared to the regular steady jet film cooling. Sweeping jet fluidic oscillators are passive and can generate a sweeping movement without the need for any moving parts. In addition, they can be more conveniently manufactured by additive manufacturing techniques. This paper presents an experimental study of employing two-phase (air/mist) flow through a row of passive fluidic oscillators in film cooling applications for gas turbine aerofoil cooling. The objective of this study is to investigate the potential enhancement of film cooling by using sweeping jets injected with water mist. Three blowing ratios (BR = 0.85, 1.46, 2.40) and two mist ratios (MR = 2.75% and 6.92%) are used (i.e., a total of nine cases including the air-only cases). Infrared thermography and E-type thermocouples were used to measure the wall temperature, while a phase Doppler particle analyzer (PDPA) was used to measure the droplets’ size distributions. The initial mean droplet size is 11.6μm. An interesting observation was found where thin water liquid streaks were formed at the exit of the fluidic oscillators and traveled for very long distances (about 140D) providing excellent local film cooling under the laboratory low heating condition. The forming of liquid streaks is due to the significant droplets coalescence phenomenon caused by large oscillating vortical flows inside the fluidic oscillator. Adding small mist ratios provided better cooling effectiveness with an overall time-averaged cooling enhancement of 15–90% and a maximum local cooling enhancement of 300–350% in all the cases studied. The sweeping jet provided better film cooling effectiveness at the centerline and spanwise direction (87% and 76%, respectively) when compared to steady jets under the laboratory conditions with low temperatures and low pressure.
Development of Innovative Low NOx Hydrogen-Fueled Burner for Aeronautic Applications
Authors: Ruan Jiangheng L. , Vincent-Randonnier Axel , Pilla Guillaume , Irimiea Cornelia
Published: September 2023

Large eddy simulations (LES) were performed to develop an innovative hydrogen-fueled burner for aeronautic applications. Hydrogen is a much cleaner fuel than classic jet fuels (hydrocarbons) since its combustion with air only produces water without any carbon compounds (soot particles, volatile organic compounds, carbon monoxide or carbon dioxide). Nevertheless, at high temperatures (i.e. over about 1800 K), nitrogen and oxygen in the air combine to produce nitrogen oxides (NOx). Low-NOx combustion then implies to achieve lean premixed conditions. Unfortunately, due to the high laminar flame speed and very lean limit of extinction of H2-air flames, hydrogen combustion is prone to flashback, thus implying to design fast mixing injectors. Lean Direct Injection (LDI) and Micromix concepts have been proposed to boost the mixing between hydrogen and air. LDI relies on rapid and uniform mixing to get a lean premixed H2-air mixture before combustion occurs, whereas Micromix concept divides the burner into several small elementary burners. In the current paper, we present the results of numerical simulations performed with an original design of a swirled injector designed to achieve stable H2-air combustion in lean-premixed conditions. However, the sole premixed injection is insufficient to stabilize combustion from idle to take-off conditions. To fix this issue, a pilot injection of fuel (i.e. generating a non-premixed flame) has been added to sustain combustion in a wide range of operating conditions. The flame produced with this burner has been investigated numerically for three operating conditions of a turboshaft engine: takeoff, cruise and idle conditions. Simulations were carried out with a 9 species and 21 steps chemical mechanism for H2-air, which was then modified to take into account the NOx formation using the Zeldovich model. Comparisons between simulations using Quasi-Laminar Model (QLM) and Thickened Flame Model (TFM) were performed. Both models lead to stable combustion for any flight conditions, with NOx emissions at about a hundred times lower than the measured level with an engine of equivalent thrust operated with kerosene Jet A-1. Finally, experiments were achieved on a semi-industrial scale test rig operated at the same conditions than CFD simulations. Thanks to the combustor optical accesses and the gas sampling probe inside the chamber, images of the flame and NOx measurements could be obtained, showing a satisfactory agreement with simulations.
Probabilistic CFD Analysis of a High-Pressure Compressor Under Consideration of Manufacturing and In-Service Variability
Authors: Schlüter Lukas , Voigt Matthias , Schmidt Robin , Becker Bernd , Mailach Ronald
Published: September 2023

The impact of geometric variability of compressor airfoils due to manufacturing scatter and operational effects on the aerodynamic performance is a well-addressed topic in the research field of turbomachinery. Thereby, the airfoils’ leading edge (LE) shapes are highly connected to their aerodynamic behavior, affecting the boundary layer development and potential shock systems. The impact of such real geometry effects can be evaluated utilizing probabilistic methods. In previous probabilistic computational fluid dynamics (CFD) analyses, the LEs are usually modeled as semi-circles or semi-ellipses, whereas their noticeable deviation from such simplified shapes is given comparatively little attention.

To overcome this shortfall a Monte Carlo simulation based probabilistic CFD analysis of a 10.5 stage high-pressure compressor is conducted under consideration of variable rotor geometries. These are described by a parametric model accounting for the airfoils’ general- and the LE shapes’ specific geometric variability. A database with more than 1000 optically measured blades is utilized for deriving median models (MMs) and the statistical distributions of the deviation from these MMs. Additionally, the assessment of the parameterization quality is based on these measurements. The CFD results are post-processed using the coefficient of importance, which allows the identification of important probabilistic input parameters and prominent rotors. The probabilistic results highlight the significance of the LE shapes’ variability. Furthermore, the impact of the sample size on the probabilistic results as well as the importance of characteristic differences within the underlying MMs are discussed.
Evaluation of Inlet Conditions of an AFT Mounted BLI Design in a Sub-Scale Test Rig
Authors: Rasimarzabadi Faezeh , Martensson Hans , Clark Catherine , Neuteboom Martin
Published: September 2023

A unique sub-scale rig for studying boundary layer ingestion (BLI) propulsion has been developed by National Research Council of Canada (NRC). The rig is capable of varying the operating pressure levels and Mach numbers independently. It consists of a boundary layer generator to simulate boundary layer development over an aircraft fuselage. The boundary layer thickness upstream of the fan blades is controlled independent of other parameters using air injected through a perforated plate. The purpose is to demonstrate the advantages of BLI in reducing the power required for a given thrust and to evaluate varying inlet conditions on BLI fan performance. This paper provides details on set-up and procedure for testing an aft-mounted, distortion-tolerant fan tested at a number of different operating conditions. The results shows how the fan speed can affect the boundary layer thickness at the nacelle inlet. Different strategies for probe traversing are evaluated to find suitable procedures for obtaining valid data. Considering that there are 24 vanes, the 36° intervals give a better representation of the average compared to 45° intervals, since the clocking relative to the stator wakes significantly affects the total pressure. The traversing has to be done individually in order to avoid that the downstream probes data be affected by the upstream probes. The numerical results are compared with the experimental data and show reasonably good agreement.
JoeRot - Rotor Dynamics Toolbox Based on Complex Transfer Matrix Method
Authors: Niş Hüseyin Tarık , Yıldız Ahmet , Kılıçaslan Alican
Published: September 2023

The demand for high-speed and high-precision lightweight rotors increases with the need for high-performance industrial machines. To manufacture such precision rotors, engineers are pushed to perform more detailed design analyses using the science of rotor dynamics. However, commercial rotor dynamics software that performs these analyses has high prices. In addition, the closed source code prevents the researcher from developing subroutines to work with their test data. These limitations in commercial software prevent researchers from solving unique rotor dynamics problems. For this reason, researchers around the world have been developing their rotor dynamics software based on the Finite Element Method (FEM). In this study, an in-house-developed & open-source rotor dynamics toolbox named JoeRot is developed based on the Complex Transfer Matrix Method (CTMM). The proposed toolbox can perform analyses faster than the FEM and allows modeling and solving unique rotor dynamics problem such as unbalance response. Various analyses such as plotting the Campbell diagram, finding natural frequencies, determining mode shapes, determining the system frequency response due to unbalance, instability threshold analysis, and plotting a critical velocity map can be carried out on the designed toolbox. To investigate the accuracy of the JoeRot toolbox, a comparison is made between the analytical method and the finite element method. As a result of this comparison, it is observed that natural frequencies and deflection frequency response values were obtained under a 0.46% error rate and 22.75 times faster than other compared methods.
Strategies for High-Accuracy Measurements of Stage Efficiency for a Cooled Turbine
Authors: Rozman Maria , Berdanier Reid A. , Barringer Michael D. , Thole Karen A.
Published: September 2023

Gas turbines are used in a broad range of aerospace and land-based applications from power generation to aviation, and their usage is projected to continue to grow. As a result, it is critical to find innovative solutions for improving turbine efficiency to reduce fuel consumption and carbon emissions. Successful demonstration of new efficiency-increasing technologies at rig or engine scale requires efficiency measurement techniques that are both accurate and repeatable. The Steady Thermal Aero Research Turbine (START) Laboratory at the Pennsylvania State University is utilizing a unique 360° traversing system for temperature and pressure probes with redundant torque measurements to quantify thermal efficiency for a single-stage cooled test turbine. The purpose of this study is to determine a measurement method that produces highly accurate and repeatable efficiency calculations. With these systems, flows in the full annulus have been analyzed and compared with subsector traverse segments centered at different circumferential positions to determine the appropriate sector size. The results from this investigation indicate that the full 360° measurement is recommended to minimize variation in calculated stage efficiencies. This study also compares the circumferential variations in thermodynamic and mechanical efficiency calculation methods, finding that the thermodynamic efficiency calculation results in a higher accuracy for full exit plane measurements. In parallel, a statistical analysis was performed to determine the number of required repeats for the full 360° traverse necessary to achieve a desired precision uncertainty that is half of the bias uncertainty. Ultimately, this study establishes guidelines to streamline experimental procedures by limiting the necessary test count per operating condition to 10 measurements. Following these procedures establishes a bias of εb = 0.18 points, and limits the precision uncertainty to at most εp = 0.09 points, resulting in a total uncertainty of at most εt = 0.20 points.
Experimental Measurements and CFD Predictions of NOx Emissions From a Water-Cooled Rotating Detonation Engine
Authors: Strakey Peter A. , Ferguson Donald H.
Published: September 2023

A water-cooled Rotating Detonation Combustor (RDC) operating on hydrogen and air and utilizing a pintle-style injector with an axial air flow path was operated over a wide range of mass flowrates, equivalence ratios and back-pressures producing a variety of wave modes. Measurements of NOx as well as O2 were conducted by sampling the combustor exhaust just downstream of the throat after the combustor reached a thermally steady-state condition.

2D RDC simulations were conducted with several detailed hydrogen-air chemical mechanisms along with detailed NO formation chemistry to investigate the sensitivity of the results to the chemical mechanisms as well as to derive a better understanding of where in the detonation wave NO is being formed.

3D simulations using a Large Eddy Simulation approach with a Partially Stirred Reactor model were conducted and validated against the experimental data. Wall heat losses were included and validated against global wall heat losses measured in the water-cooled RDC. While the simulations generally predicted higher NOx emissions than what was measured, the trends with equivalence ratio were well predicted.

The implications of this study are that NOx emissions from RDCs are not unreasonably high and CFD can be used to predict NOx emissions as well as to optimize injector geometry. Selection of an appropriate NOx chemistry sub-model along with experimental validation is key to improving the reliability on the simulations.
A Surge/Stall-Capable Dynamic Performance Simulation Methodology for a Turbojet Engine
Authors: Güllü Emrah , Aran Gökhan
Published: September 2023

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

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

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

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

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

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

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

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

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