bluuebunny/crossref_metadata_2025 huggingface dataset:
Rural Veterans with HIV and Alcohol Use Disorder receive less video telehealth than urban Veterans
Authors: Sheinfil Alan Z , Day Giselle , Walder Annette , Hogan Julianna , Giordano Thomas P. , Lindsay Jan , Ecker Anthony
Published: September 2023

Purpose

Alcohol use disorder (AUD) is highly prevalent among Veterans with HIV. Rural Veterans with HIV are at especially high risk for not receiving appropriate treatment. This retrospective cohort cross‐sectional study aimed to investigate patterns of mental health treatment utilization across delivery modality among Veterans diagnosed with HIV and AUD. It was hypothesized that rural Veterans with HIV and AUD would receive a lower rate of mental health treatment delivered via video telehealth than urban Veterans with HIV and AUD.

Methods

A national Veterans Health Association administrative database was used to identify a cohort of Veterans diagnosed with HIV and AUD (N = 2,075). Geocoding was used to categorize rural Veterans (n = 246) and urban Veterans (n = 1,829). Negative binomial regression models tested associations between rurality and mental health treatment delivered via face‐to‐face, audio‐only, and video telehealth modalities.

Findings

Results demonstrated that rural Veterans with HIV and AUD received fewer mental health treatment sessions delivered via telehealth than urban Veterans with HIV and AUD (incidence rate ratio = 0.62; 95% confidence intervals [0.44, 0.87]; P < .01). No differences were found in terms of treatment delivered face‐to‐face or by audio‐only.

Conclusions

Rural Veterans with HIV and AUD represent a vulnerable subpopulation of Veterans who may most benefit from video telehealth. Efforts to increase access and improve the uptake of evidence‐based mental health treatment delivered via video telehealth are needed.
Arabidopsis leaf‐expressed AGAMOUS‐LIKE 24mRNA systemically specifies floral meristem differentiation
Authors: Huang Nien‐Chen , Tien Huan‐Chi , Yu Tien‐Shin
Published: September 2023

Plants can record external stimuli in mobile mRNAs and systemically deliver them to distal tissues to adjust development. Despite the identification of thousands of mobile mRNAs, the functional relevance of mobile mRNAs remains limited.

Many mobile mRNAs are synthesized in the source cells that perceive environmental stimuli, but specifically exert their functions upon transportation to the recipient cells. However, the translation of mobile mRNA‐encoded protein in the source cells could locally activate downstream target genes. How plants avoid ectopic functions of mobile mRNAs in the source cells to achieve tissue specificity remains to be elucidated.

Here, we show that Arabidopsis AGAMOUS‐LIKE 24 (AGL24) is a mobile mRNA whose movement is necessary and sufficient to specify floral organ identity. Although AGL24 mRNA is expressed in vegetative tissues, AGL24 protein exclusively accumulates in the shoot apex. In leaves, AGL24 proteins are degraded to avoid ectopically activating its downstream target genes.

Our results reveal how selective protein degradation in source cells provides a strategy to limit the local effects associated with proteins encoded by mobile mRNAs, which ensures that mobile mRNAs specifically trigger systemic responses only in recipient tissues.
Development of a risk prediction model for surgical site infection after lower third molar surgery
Authors: Yamagami Akira , Narumi Katsuya , Saito Yoshitaka , Furugen Ayako , Imai Shungo , Kitagawa Yoshimasa , Ohiro Yoichi , Takagi Ryo , Takekuma Yoh , Sugawara Mitsuru , Kobayashi Masaki
Published: September 2023

Background

There is little evidence regarding risk prediction for surgical site infection (SSI) after lower third molar (L3M) surgery.

Methods

We conducted a nested case–control study to develop a multivariable logistic model for predicting the risk of SSI after L3M surgery. Data were obtained from Hokkaido University Hospital from April 2013 to March 2020. Multiple imputation was applied for the missing values. We conducted decision tree (DT) analysis to evaluate the combinations of factors affecting SSI risk.

Results

We identified 648 patients. The final model retained the available distal space (Pell & Gregory II [p = 0.05], Pell & Gregory III [p < 0.01]), depth (Pell & Gregory B [p < 0.01], Pell & Gregory C [p < 0.01]), surgeon's experience (3–10 years [p = 0.25], <3 years [p < 0.01]), and simultaneous extraction of both L3M [p < 0.01]; the concordance‐statistic was 0.72. The DT analysis demonstrated that patients with Pell and Gregory B or C and simultaneous extraction of both L3M had the highest risk of SSI.

Conclusions

We developed a model for predicting SSI after L3M surgery with adequate predictive metrics in a single center. This model will make the SSI risk prediction more accessible.
Philippine immunization coverage and dengvaxia: An infodemiological study
Authors: Jamora Roland Dominic G. , Lim Marie Abigail R. , Espiritu Adrian I.
Published: September 2023

Background

A dengue vaccine, dengvaxia, was licensed for the first time in 2015. It was approved for use in 11 countries where dengue infection is endemic, including the Philippines. In November 2017, controversy arose in the Philippines regarding the dengvaxia vaccine. We hypothesized that the dengvaxia controversy might be correlated with immunization coverage in the Philippines.

Methods

We performed an analytical and infodemiological study on web‐based interest in dengvaxia, both globally and in 18 dengue endemic countries, from 2015 to 2020 using Google Trends™. Comparisons were made with search trends for the components of the National Immunization Program (NIP) and vaccine coverage by computing the Pearson product–moment correlation coefficient (r) between each variable.

Results

Among the 18 countries included, the Philippines had the highest search volume index for dengvaxia, with peaks in searches coinciding with that of worldwide search trends. There was no correlation between the relative search volume for dengvaxia with that of vaccines included in the NIP in the Philippines from 2015 to 2020. There was no significant correlation between web‐based interest in dengvaxia and the estimated immunization coverage from 2015 to 2019.

Conclusion

There was no significant correlation between web‐based interest in dengvaxia, the vaccines in the NIP, and national immunization coverage.
How to be minimalist about shared agency
Authors: Salomone‐Sehr Jules
Published: September 2023

What is involved in acting together with others? Most shared agency theorists endorse the Shared Intention Thesis, i.e., the claim that shared agency necessarily involves shared intentions. This article dissents from this orthodoxy and offers a minimalist account of shared agency—one where parties to shared activities need not form rich webs of interrelated psychological states. My account has two main components: a conceptual analysis of shared agency in terms of the notion of plan, and an explanation of undertheorized agency‐sharing mechanisms. My analysis states that we act together just in case our activities conform to a plan and that plan figures in an explanation of our activities’ joint conformity to it. To sloganize: shared activity is plan‐coordinated activity. Sometimes, plan‐coordination goes by way of shared intentions. However, besides shared intentions, there are at least two additional families of agency‐sharing mechanisms. The first features a central planner who determines the content of a plan and attributes the different parts of that plan to a collection of agents. The second does away with the planner and involves a roughly Darwinian selection of patterns of activity. Both families of mechanisms enable us to act together even in the absence of shared intentions.
Supra and subgingival application of antiseptics or antibiotics during periodontal therapy
Authors: Figuero Elena , Serrano Jorge , Arweiler Nicole Birgit , Auschill Thorsten Mathias , Gürkan Ali , Emingil Gülnur
Published: September 2023

Periodontal diseases (gingivitis and periodontitis) are characterized by inflammatory processes which arise as a result of disruption of the balance in the oral ecosystem. According to the current S3 level clinical practice guidelines, therapy of patients with periodontitis involves a stepwise approach that includes the control of the patient's risk factors and the debridement of supra and subgingival biofilm. This debridement can be performed with or without the use of some adjuvant therapies, including physical or chemical agents, host modulating agents, subgingivally locally delivered antimicrobials, or systemic antimicrobials. Therefore, the main aim of this article is to review in a narrative manner the existing literature regarding the adjuvant application of local agents, either subgingivally delivered antibiotics and antiseptics or supragingivally applied rinses and dentifrices, during the different steps in periodontal therapy performed in Europe.
Marked reduction in the incidence of transfusion‐transmitted hepatitis B virus infection after the introduction of antibody to hepatitis B core antigen and individual donation nucleic acid amplification screening in Japan
Authors: Tanaka Ami , Yamagishi Naoji , Hasegawa Takashi , Miyakawa Keiko , Goto Naoko , Matsubayashi Keiji , Satake Masahiro
Published: September 2023

Background

In Japan, 41 million blood donations have been screened for hepatitis B virus (HBV) during the past 8.4 years using individual donation nucleic acid amplification testing (ID‐NAT) and antibody to hepatitis B core antigen (anti‐HBc) screening.

Study Design and Methods

Transfusion‐transmitted HBV infection (TT‐HBV) incidence was examined. Donated blood implicated in TT‐HBV was analyzed for infection stage and DNA levels. Causative HBV strains were phylogenetically analyzed.

Results

Among 5162 (0.013%) ID‐NAT positives, window period (WP) and occult HBV infection (OBI) accounted for 3.4% (176) and 11.5% (594), respectively. No OBI‐related TT‐HBV occurred. Seven blood donations caused eight TT‐HBV cases, six of which were in the pre‐ID‐NAT WP, leaving one with an unresolved infection stage. Seven cases were caused by platelet concentrate (180 mL plasma) and one case by fresh‐frozen plasma (200 mL plasma), which contained estimated infectious doses varying between 2 and 2300 HBV virions. HBV subgenotypes in five cases were HBV/A2. Complete genome sequences of the transmitting A2 strains were nearly identical (99.6%–100%) and clustered in a group that included HBV/HIV‐1 coinfections and a higher proportion of donors in the acute infection phase (69%) than the other group of HBV/A2 sequences (5%).

Discussion

The incidence of observed TT‐HBV cases has significantly reduced to 0.19 per million in the ID‐NAT screening period. OBI‐related TT‐HBV was eliminated by anti‐HBc screening. Established TT‐HBV cases were caused by blood products with large plasma volumes containing extremely low HBV concentrations derived from blood donors at a very early infection stage.
Lineamientos para la aplicación del control inmediato de legalidad en el contexto de estados de excepción
Authors: Córdoba Granda Paola Andrea , Ramírez Arias Nohelia
Published: September 2023

Este artículo es producto de la investigación que aborda el análisis normativo del control inmediato de legalidad de los actos administrativos de carácter general, expedidos por las entidades territoriales, en el marco del estado de excepción declarado con ocasión de la pandemia por la covid-19, consagrado en el artículo 136 de la Ley 1437 de 2011. Luego de abarcar los conceptos jurídicos necesarios para el mejor entendimiento de la norma, se realizó un estudio de los actos sometidos a control de legalidad ante el Tribunal Administrativo de Cundinamarca por parte de los municipios de Bojacá, Chía, Fómeque y Soacha, durante el estado de excepción de emergencia económica, social y ecológica declarado por medio del Decreto Legislativo 417 de 2020, con vigencia del 17 de marzo al 15 de abril de 2020, lo que permitió establecer que en la práctica la aplicación del medio de control presenta dificultades, tanto a nivel territorial como para el operador jurídico, siendo necesario formular criterios que permitan, a las entidades municipales y despachos judiciales, la aplicación uniforme de este, en aras de garantizar la satisfacción de los principios de eficacia y eficiencia, y la correcta y pronta administración de justicia y seguridad jurídica.
Macroscopic and Microscopic Spray Characteristics of Dimethyl Ether in a Constant Volume Spray Chamber Using a Mechanical Fuel Injection System for Automotive Applications
Authors: Agarwal Avinash Kumar , Kumar Vikram , Mehra Shanti , Mukherjee Nalini Kanta , Valera Hardikk , Nene Devendra
Published: September 2023

Spray investigations are critical for understanding internal combustion engine combustion. Optimised spray atomisation helps improve engine output/performance and reduce tailpipe emissions. The spray from the injector nozzle depends on nozzle hole diameter, fuel injection pressure, ambient density, pressure and temperature in the spray chamber, and test fuel properties. This study evaluated macroscopic and microscopic spray characteristics of dimethyl ether (DME) and baseline diesel under atmospheric conditions (1.013 bar pressure at 298 K temperature). It correlated the spray parameters with distinctive physicochemical properties of diesel and DME using dimensionless numbers, namely Reynolds number, Weber number, and Ohnesorge number. The fuel injection system consisted of a high-pressure mechanical injection pump and mechanical fuel injectors having an original equipment manufacturer fixed nozzle opening pressure in the constant volume spray chamber. The microscopic spray investigations were performed using a phase Doppler interferometer along the spray direction at three axial distances (50, 70, and 90 mm) from the nozzle. The three orthogonal spray droplet velocities of diesel and DME were compared. The droplet number-size distributions for baseline diesel and DME were compared. Macroscopic spray characteristics were evaluated using high-speed imaging. Reynolds number was higher for DME, leading to more turbulence in the spray and accelerating the spray breakup phenomenon. Weber number of DME was also much higher than baseline diesel due to its lower surface tension. The higher Weber and lower Ohnesorge numbers justified the finer droplets of DME sprays. DME showed superior spray atomization characteristics than baseline diesel, leading to superior fuel–air mixing and efficient and sootless combustion.
Leakage and Rotordynamic Force Coefficients of a Labyrinth Seal and a Pocket Damper Seal Operating With Wet Gas
Authors: Torres Jose , San Andrés Luis
Published: September 2023

Subsea centrifugal compressors commonly using labyrinth seals (LS) and pocket damper seals (PDS) must withstand the flow of oil in gas mixtures with a liquid volume fraction (LVF) up to 5%. This paper presents experimental results for the leakage and rotordynamic coefficients of a uniform clearance PDS and a similar size LS both supplied with wet gas. The shaft diameter D = 127 mm and the seal axial length L = 48 mm. In the tests, the seals’ pressure ratio (inlet/exit) = 2.5 and the shaft speed reaches 5.25 krpm (surface speed = 35 m/s). The LS has a 17% larger radial clearance (Cr,LS = 0.230 mm > Cr,PDS = 0.196 mm) due to a manufacturing error. This paper extends prior work by Torres et al. [1] for the same two seal types with a stepped clearance configuration that promotes damping. When supplied with a dry gas, the LS leaks more because of its larger clearance. A loss coefficient (cd) is a fraction of the physical clearance that characterizes a seal’s effectiveness to reduce leakage. The cd of both seals is nearly identical for operation with pure gas; the small differences are well within the experimental uncertainty. For operation with wet gas, the PDS cd decreases as the LVF increases whereas the LS cd increases, thus indicating the PDS is more effective to restrict wet gas leakage. When operating with pure gas, the direct stiffness (K) and effective damping (Ceff) of both seals are small in magnitude (K < 0.5 MN/m, Ceff < 2 kN-s/m) and often less than the experimental uncertainty. For wet gas operation and with shaft speed = 3 krpm and 5.25 krpm, the PDS produces Ceff < 0 for whirl frequencies below 50 Hz. In contrast, the LS Ceff > 0, although small in magnitude. The experimental results under wet gas operation are similar for operation with LVF equal to 3% and 5%. Unexpected low frequency broadband motions appear when supplying the PDS with a wet gas. Although small in amplitude (< 5 μm), the motions increase in severity as the mixture inlet LVF and shaft speed increase. The motions are entirely absent for tests with the LS. Experiments in which the mixture is drawn from the PDS cavities rule out liquid accumulation as the cause of the observed motions. The current test results serve as a reference for turbomachinery design engineers and aid in the validation of analytical predictive tools.
Effects of Turbine Blade Tip Pressure Side Winglet and Cavity Rim on Aerodynamic Performance
Authors: Jo SooHyun , Jeon Youngmin , Baek Seungchan , Song Jeonghwan , You Donghyun , Hwang Wontae
Published: September 2023

Turbine blade tip leakage flows occur between the unshrouded rotor and stationary casing. Such flow is one of the main sources of aerodynamic loss in a turbine. Many different methods have been proposed to reduce this loss, including the squealer tip and winglet design. In this study, numerical analysis showed that a large fraction of the leakage flow occurs after 50% of the axial chord. Thus, an additional rim was installed at the mid-point of the cavity, in an attempt to block the leakage flow to the suction side and redirect it back to the pressure side. The effect of an extended pressure-side winglet was also investigated and compared with the base squealer tip. The passage velocity field between the blades of a linear cascade was measured at 0, 25, 50, 75, and 100% of the axial chord using a 5-hole probe to assess the development of flow structures responsible for the tip leakage loss. The total pressure loss coefficient distribution was measured downstream of the cascade. Performance results from the different tip geometries were experimentally compared with each other, and also used to validate the numerical results. The winglet design showed the best performance. This design does not have a pressure-side rim, and thus the tip leakage flow has less hindrance passing over the suction-side rim, which creates a strong coherent tip leakage vortex compared to that of the squealer tip. This leads to an increase in loss beyond 90% of the span, but the counter-rotating tipwall passage vortex underneath interacts with the tip leakage vortex to reduce the loss in the 70–80% span region by a greater extent. Therefore, the pressure-side winglet design has an overall loss that is 28.3% smaller than that of the baseline squealer tip. The additional cavity rim did not show any noticeable improvements, possibly due to the angle at which it was placed, and thus needs further investigation.
Attenuation of Detrimental Hub Leakage Effects in an Axial Compressor Rotor by Customized Geometrical Design Features
Authors: Petermann Jannik , Schulz Kevin , Becker Bernd , Gümmer Volker
Published: September 2023

The aerodynamic impact of hub gap leakage on the performance characteristics of an axial compressor rotor in conventional design (no blisk) with a high hub-to-tip ratio has been investigated using three-dimensional steady-state RANS simulations. The inclusion of circumferential hub gaps in front of the leading edge and after the trailing edge, as well as inter-platform leakage, reduced the total pressure ratio and the polytropic efficiency of the rotor by as much as 3.74% and 3.97%, respectively, compared to a design case with clean endwalls. Potential design recommendations in terms of improved aerodynamic robustness against leakage effects were derived from the separate sealing of each hub gap. Six geometry modifications were assessed, which based on these results. In a throttled operating condition, large edge radii in the front gap on the disk and platform partially recovered the initial losses of both the total pressure ratio (17.7%) and polytropic efficiency (19.6%). A circular lateral platform shape with the opening pointing toward the blade’s pressure side showed superior loss recovery capabilities at a dethrottled operating point. The combination of both features did not reduce the losses further. However, the circular lateral platform shape combined with smaller front gap chamfers proved more beneficial in a throttled state.
Characterizing Shrouded Stator Cavity Flow on the Performance of a Single-Stage Axial Transonic Compressor
Authors: Shao Runzhu , He Xiao , Zhu Mingmin , Klausmann Fabian , Teng Jinfang
Published: September 2023

Shrouded stator cavity flow increases the stator total pressure loss, reduces the compressor isentropic efficiency and thus limits the compressor pressure rise capability. This paper proposes a simplified cavity flow model that consists of flow injection at the stator inlet and flow suction at the stator outlet. Based on this model, a full-factorial parametric study on the leakage flow ratio and the leakage swirl angle is performed at different rotational speeds and incidences. In the first place, the effectiveness of the numerical method is validated against the experimental data based on the full-scale cavity geometry; then, the numerical simulations on the simplified cavity geometry are validated against that of the full-scale one. Results show that the leakage flow ratio plays a dominant role in determining the compressor performance penalty. The isentropic efficiency drops almost linearly with the leakage flow ratio due to deteriorated near-hub separations, and the slope becomes steeper at higher operating speeds and incidences. The leakage swirl angle only has a pronounced effect under a high leakage flow ratio. The efficiency penalty reduces with increasing swirl angle due to an alleviated tangential flow mixing and suppressed near-hub separations. The swirl angle effect is more pronounced at lower incidence conditions. These findings advance the fundamental understanding of shrouded stator cavity flow effects and provide useful guidance for cavity seal designs.
Pressure Loss Analysis and its Prediction in Typical Valve Designs for Steam Turbines
Authors: Slama Vaclav , Rudas Bartolomej , Šimurda David , Hála Jindřich
Published: September 2023

Pressure loss analysis in valve assemblies for steam turbines has always been one of the traditional issues in order to enhance the valve design to ensure safe operation, reasonable price, and, especially, reduce pressure losses hence increasing the whole turbine output. Besides, during the preliminary turbine design, the efficiency should be predicted as accurately as possible. For this reason, the results based on a comprehensive range of measurements and numerical simulations should be compared with a general flow theory in the valves. Although many results have already been presented, the theoretical analysis and its confrontation with experimental and numerical results in the form of total loss and flow contraction coefficients have not been presented so far. It is the primary motivation of this paper. The total loss coefficient in the valve is compared with the total loss coefficient in the diffuser with and without flow detachment. Differences are described in the form of loss increase coefficient in the valve. Furthermore, in order to describe the influence of wakes and flow field non-uniformity under the valve cone, the flow contraction coefficient is introduced. The analysis is carried out on the two most typical valve assemblies: an assembly with one control valve in the chamber and an assembly with two control valves in the chamber. Data were obtained from measurements on the valve model and numerical simulations. The measurements were carried out on a valve model installed in an in-draft wind tunnel for high speeds in the Aerodynamic laboratory of the Institute of Thermomechanics of the Czech Academy of Sciences. The numerical simulations were carried out in the Doosan Skoda Power Company using a package of ANSYS software tools. Evaluated data complement each other. Generalized results allow us to easily predict mass flows and pressure losses and compare different valve designs from the efficiency point of view.
Large Eddy Simulation of Soot Formation in a Real Aero-Engine Combustor Using Tabulated Chemistry and a Quadrature-Based Method of Moments
Authors: Koob Philipp , Ferraro Federica , Nicolai Hendrik , Eggels Ruud , Staufer Max , Hasse Christian
Published: September 2023

Considering the increasingly stringent targets for aircraft emissions, CFD is becoming a viable tool for improving future aero-engine combustors. However, predicting pollutant formation remains challenging. In particular, directly solving the evolution of soot particles is numerically expensive. To reduce the computational cost but retain detailed physical modeling, quadrature-based moments methods can be efficiently employed to approximate the particle number density function (NDF). An example is the recently developed split-based extended quadrature method of moments (S-EQMOM), which enables a continuous description of the soot particles’ NDF, essential to consider particle oxidation accurately. This model has shown promising results in laminar premixed flames up to turbulent laboratory scale configurations. However, the application to large-scale applications is still scarce. In this work, the S-EQMOM model is applied to the Rolls-Royce BR710 aero-engine combustor to investigate the soot evolution process in practically relevant configurations. For this, the soot model is embedded into a high-fidelity simulation framework, consisting of large eddy simulation for the turbulent flow and mixing and the flamelet generated manifold method for chemistry reduction. An additional transport equation for polycyclic aromatic hydrocarbons is solved to model their slow chemistry and the transition from the gaseous phase to the solid phase. Simulations are performed for different operating conditions (idle, approach, climb, take-off) to validate the model using experimental data. Subsequently, the results are analyzed to provide insights into the complex interactions of hydrodynamics, mixing, chemistry, and soot formation.
Crossflow Minimization for Jet Impingement Cooling Applications
Authors: Salem Abdel Rahman , Soliman Ibrahim , Amano Ryoichi S.
Published: September 2023

Jet impingement is used to efficiently cool gas turbine blades and other engine components. However, jet-to-jet interactions result in the accumulation of crossflow as the spent air migrates downstream, which usually causes a decay in the Nusselt number and reduces the overall cooling performance. In this study, several crossflow mitigation techniques are investigated by attaching small and easy-to-manufactured crossflow diverters to protect jet cores from upstream crossflows and, therefore, enhance heat transfer performance. Three diverter shapes of cylindrical, rectangular, and ribbed type are studied within a 25-jet array under laminar and turbulent flow regimes (Rej of 2,500–10,000). Three-dimensional Navier-Stokes (N-S) equations are solved under the k-ɛ turbulence model following a mesh sensitivity study. Diverter heights of 25%, 50%, and 75%, as a percentage of jet-to-target spacing denoted as quarter-length (QL), half-length (HL), and three-quarter-length (TQL), respectively, are considered with a constant heat flux condition. Results show an increase in average Nusselt number values from 6.6% to 12% achieved by a TQL cylindrical-shaped diverter. However, the associated friction factor is also increased by 9.9%–24.3% on average compared to the baseline model. Nevertheless, the heat transfer performance parameter (η) is introduced to quantify the desired gain in Nu and the cost in the pressure loss. Consequently, results show a net enhancement of up to 5.2%, 3.1%, and 3.8% for cylindrical, rectangular, and ribbed-type diverters, respectively.
CFD Parameter Studies Using an Actuator Disk to Quantify the Interactions on an Airfoil Segment for Distributed Propulsion
Authors: Kirsch Bastian , Friedrichs Jens
Published: September 2023

In this study, CFD parameter variations are performed to investigate propeller-wing interactions. For this purpose, the solver TAU of the German Aerospace Center with the integrated Actuator Disk is used. The 2.5D setup studied consists of a wing segment with constant chord length and an Actuator Disk iterated to a constant thrust in all cases. The parameters to be varied are: Position, rotational speed, installation angle and segment width. Lift and drag coefficients and propeller efficiencies are used as result variables. It can be seen that the position of the propeller, its installation angle and the spanwise distance between the propellers have significant influence on the interactions. The rotational speed has hardly any influence on the interactions in the considered range. Positions above the wing chord benefit from high lift coefficients, but at the same time drag increases. An exception is the position centrally above the wing, which is characterized by a strong drag reduction in all parameter combinations. Positions above the leading and trailing edge of the wing show also strong sensitivities to the installation angle. Reducing the distance between the propellers amplifies the existing trends, so that advantages are higher, but disadvantages are also more pronounced.
Detailed Gaseous and Particulate Emissions of an Allison 250-C20B Turboshaft Engine
Authors: Rohkamp Marius , Rabl Alexander , Gündling Benedikt , Saraji-Bozorgzad Mohammad Reza , Mull Christopher , Bendl Jan , Neukirchen Carsten , Helcig Christian , Adam Thomas , Gümmer Volker , Hupfer Andreas
Published: September 2023

Aviation is known to be one of the most significant contributors to air pollutants. This includes gaseous emissions, like carbon-dioxide (CO2) and nitrogen oxides (NOx), and also particulate matter (PM), especially in the form of soot. This study conducted emission measurements on an Allison 250-C20B turboshaft engine operating on Jet A-1 fuel with a focus on gaseous compounds (e.g. ozone precursors) and PM, regarding their number and mass concentration. The different engine loading points were chosen based on the percentage thrust ratios of the International Civil Aviation Organization (ICAO) Landing and Take-Off-Cycle (LTO-Cycle). A standard FTIR/O2/FID system to measure general combustion compounds e.g. CO2, carbon-monoxide (CO), unburned hydrocarbons (UHC), and NOx, was used for the gaseous measurements. For the investigation of the volatile organic compounds (VOC), which are known to act as ozone precursors, a gas-chromatograph (GC) was applied. Different measurement methods were used to characterize the PM emissions. For the particle size distribution (PSD), we used two types of electrical mobility analyzers (SMPS and DMS500) and an aerodynamic aerosol classifier (AAC). All measurement systems yielded comparable PSD results, indicating reliable results. The particle measurement methods all show increasing aerosol diameter modes (electrical and aerodynamic) with increased engine loading. The aerosol diameter modes were shifting from 29 nm to 65 nm. Furthermore, the size and shape of different individual particles were evaluated with a scanning electron microscope (SEM). In addition, a correlation between the injection system and the particle formation was established. Gaseous turboshaft engine emissions show high CO and UHC values in Ground Idle (GI) level. NOx levels were the highest at Take-Off (TO) conditions. Acetylene and ethylene were the most significant contributors to ozone formation.
A Numerical Test Rig for Turbomachinery Flows Based on Large Eddy Simulations With a High-Order Discontinuous Galerkin Scheme - Part 3: Secondary Flow Effects
Authors: Morsbach Christian , Bergmann Michael , Tosun Adem , Klose Björn F. , Bechlars Patrick , Kügeler Edmund
Published: September 2023

In this final paper of a three-part series, we apply the numerical test rig based on a high-order Discontinuous Galerkin scheme to the MTU T161 low pressure turbine with diverging end walls at off-design Reynolds number of 90,000, Mach number of 0.6 and inflow angle of 41°. The inflow end wall boundary layers are prescribed in accordance with the experiment. Validation of the setup is shown against recent numerical references and the corresponding experimental data. Additionally, we propose and conduct a purely numerical experiment with upstream bar wake generators at a Strouhal number of 1.25, which is well above what was possible in the experiment. We discuss the flow physics at midspan and in the end wall region and highlight the influence of the wakes from the upstream row on the complex secondary flow system using instantaneous flow visualization, phase averages and modal decomposition techniques.
Gas Concentration Maps Within a Turbomachine Combustor Fueled With Jet-A1 or Sustainable Aviation Fuel (SAF)
Authors: Jarin Jean-Baptiste , Champion-Réaud Jean-Louis , Lambert Pierre-Alain , Mendes Carlos , Jeuland Nicolas , May-Carle Jean-Baptiste , Doucet Clarisse , Picard Florent
Published: September 2023

From July to September 2021, a test campaign was performed by Safran Tech and of the university of Pau E2S (Energy & Environment Solutions lab), on a MAKILA 2B turboshaft (rated 2200 shp). For this purpose, the engine was fueled with a 100% Non-Drop In Sustainable Aviation Fuel (SAF) manufactured by TotalEnergies from Used Cooking Oil (UCO) through the Hydro-Esterification of Fatty Acids process (HEFA). The key objective of this test campaign, which was concluded by a 1st flight realized by Airbus Helicopters on Nov. 9th 2021 [1], was to compare the performance and emissions of CAF (Conventional Aviation Fuel, i.e. regular Jet-A1 manufactured from fossil fuel) and a 100% Sustainable Aviation Fuel on a turboshaft which is a reference in the helicopter industry. The results achieved allow to draw a first comparison. The ground tests concluded to the absence of any major differences in terms of engine performances (Power generation, ignition, lubrication, heat exchange, ...) between SAF and CAF. This was later confirmed by Airbus Helicopters during the flight tests. Tests showed reduced CO2 emissions explained by the higher Hydrogen to Carbon ratio (H/C) of the fuel. A significant reduction of the Smoke Number (SN), −60%, is recorded and explained by the lack of aromatics in the fuel. At this stage, it is not possible to conclude that a total lack of aromatics provides the highest reduction of SN and an optimization could be refined, as proposed by Vamsikrishna Undavalli & al. [2]. This will be further investigated in future research projects by Safran and TotalEnergies.
Study on Aerothermal Performance of a High Temperature VG Turbocharger
Authors: Kitamura Tsuyoshi , Yoshida Kazuki , Danmoto Yosuke , Nakagawa Hiroshi , Hoshi Toru
Published: September 2023

This paper is intended as the evaluation of the aerothermal performance of a high temperature VG (Variable Geometry) turbocharger, which is installed in gasoline engines for small passenger vehicles. The turbine performance with thermal energy loss is discussed through CFD and CHT (Conjugate Heat Transfer) calculations for the VG turbocharger. The CHT calculations with detailed modeling of a VG turbocharger were executed to acquire the whole thermal and flow field accurately. Heat flow from the turbine section to the bearing housing with water cooling has also been simulated.

In addition, the bench tests for the VG turbocharger were conducted to validate the CHT calculations. Analytical results provided good agreement with experimental data. Eventually, the performance degradation induced by thermal energy loss has been evaluated.
Computational Fluid Dynamics in a Fan-Drive Gear System of an Aeroengine
Authors: Hashimoto Hironori , Arisawa Hidenori , Kondo Koki , Shinoda Yuji , Tanaka Mitsuaki , Imai Hideyuki , Fujii Isao , Nishida Takunobu
Published: September 2023

To reduce fuel consumption of aeroengines, gearing of engines has become a trend. In geared engines, a design based on the elucidation of phenomena is necessary to achieve both high efficiency and reliability. Therefore, computational fluid dynamics (CFD) can contribute effectively to optimize its design. However, to our knowledge, examples of numerical simulation of high-speed gas-liquid two-phase flow in a planetary gear system, including multiple gear meshes and structures for oil capture, are not available in literature.

Therefore, in this study, a numerical simulation method, previously developed by our research team, was used for a planetary gear system. The key feature of our numerical simulation method is that it realizes fast and numerically stable calculations by using the volume of fluid (VOF) method and surface compression scheme for the air-liquid interface, and the porosity method for the object boundary.

To validate the accuracy of the numerical simulation method used, a planetary gear system with specifications equivalent to those of an aeroengine gear system was used. The numerical simulation and experimental test results obtained were then compared for fluid dynamic loss and oil capture flow rate. From this comparison, it was confirmed that the numerical simulation method used has a practically acceptable accuracy.

The effects of the shape of the oil capture structure on the fluid dynamic loss and oil capture flow rate were investigated using our numerical simulation. The relationship between air flow, oil flow, and fluid dynamic loss, as well as the relationship with the oil capture flow rate were then discussed.
Gradient-Free Aerodynamic Optimization With Structural Constraints and Surge Line Control for Radial Compressor Stage
Authors: Schaffrath Robert , Nicke Eberhard , Forsthofer Nicolai , Kunc Oliver , Voß Christian
Published: September 2023

The concept and design of High Temperature Heat Pumps (HTHP) including their components for specific temperature needs is a time consuming and interdisciplinary task. Especially, the design of compressor geometries has a big impact on the overall performance and the initial costs of the system. For this reasoning, in this work an automated aerodynamic gradient-free optimization including structural constraints for the geometry of a radial compressor impeller blade as well as diffusor vane geometry for water steam, that is applied in a reverse Rankine cycle based HTHP, is presented. Objective of the optimization is the isentropic efficiency in the aerodynamic design point (ADP) of the compressor. Constraints for the pressure ratio, mass flow rate and limits for stresses in blade and disk geometry satisfy requirements of the cycle simulation of the whole HTHP system and structural needs. The optimization method is based on evolutionary algorithms and stochastical surrogate models. Additionally, a highly throttled operating point is regarded to achieve an acceptable distance to the surge line. These types of optimization problems are often characterized by lots of unconverged iterations due to unstable computational fluid dynamic simulations (CFD). To encounter this, a study of the optimization process with different surrogate models is presented. The results are discussed with respect to convergence history as well as objective and constraint improvement.
Friction Saturated Limit Cycle Oscillations – Test Rig Design and Validation of Numerical Prediction Methods
Authors: Schwarz Stefan , Reil Johannes , Gross Johann , Hartung Andreas , Rittinger David , Krack Malte
Published: September 2023

In this paper, an experimental test rig for friction saturated limit cycle oscillations is proposed to provide a validation basis for corresponding numerical methods. Having in mind the application of turbine blades, an instrumented beam-like structure equipped with an adjustable velocity feedback loop and dry frictional contacts is designed and investigated. After dimensioning the test rig by means of a simplified one dimensional beam model and time domain simulations, the specific requirements of limit cycle oscillations for the design of the frictional contact, the velocity feedback loop and the excitation system are discussed and possible solutions are presented. Also appropriate measuring principles and evaluation techniques are assessed. After commissioning of the test rig, the influence of the negative damping and the normal contact force on the limit cycle oscillations is measured and the practical stability is investigated. The test rig shows linear dynamics for sticking contact and highly repeatable limit cycles. The measured results are discussed regarding the consistency with theory and compared to the predictions of a three dimensional reduced order model solved in frequency domain by the harmonic balance solver OrAgL. It is demonstrated that the numerical modeling strategy is able to accurately reproduce the measured limit cycle oscillations, which stabilized for different contact normal forces and self-excitation levels.
Wind-Turbine Inspection, Maintenance and Repair Robotic System
Authors: Cieslak Chris , Shah Aksat , Clark Brodie , Childs Peter
Published: September 2023

World-wide wind energy capacity continues to grow with 1870 TW h in 2021, with annual additions of 113 GW in 2020 and 59 GW in 2019 with over 90% of the growth as a result of offshore wind farm installations. To attain 2050 net zero targets annual capacity additions of 250 GW are expected. Wind turbine assets require regular inspection and maintenance to ensure performance, compliance to standards and insurance requirements. A range of approaches are used in inspection and maintenance including airborne and platform mounted technologies, robots, as well as accessing the blades directly with rope assisted technicians. In addition to reviewing the merits and challenges associated with a range of approaches to offshore horizontal axis wind turbine maintenance this paper describes the design, trialling and in-service operation of a hexapod robot, along with options for its deployment. The robot is capable of deploying a wide range of measuring equipment and maintenance tools. The hexapod gait employed enables the chassis to be an end-effector, avoiding the use of traditional robot arms and the multiple degrees of freedom associated with the robot legs enable the robot to walk on both convex and concave surfaces as well as straddle a leading-edge profile on a wind turbine aerofoil. The robots have demonstrated functionality through multiple blade walks and tasks such as lightning protection system verification, inspections and blade surface treatments. The robot has the capability to work independently or alongside rope-assisted technicians.
Evaluation of Cooling Requirements for Rotating Detonation Combustors
Authors: Sandri Umberto , Ramanagar Sridhara Shreyas , Andreini Antonio , Bohon Myles D. , Picchi Alessio , Facchini Bruno
Published: September 2023

In the last decade, the Rotating Detonation Combustor (RDC) has received growing attention among the different Pressure Gain Combustion concepts due to the simplicity of the design and the potential ease of integration in gas turbines. However, multiple technological challenges are still associated with its development. Researchers have pointed out concerns related to the heat loads determined by the high temperature and the complex flow field occurring in this kind of combustion chamber based on a small but meaningful set of experimental and numerical results. An investigation of the open literature has shown a strong sensitivity of the heat loads with multiple designs and operational parameters. The aim of this work is to provide a fundamental review of the primary drivers affecting heat load in a typical RDC in order to define basic cooling requirements for possible actual design of the combustor. Along with this, a simplified approach has been implemented for the estimation of the requirements for cold side convection cooling with respect to different heat load scenarios, shedding light on the compatibility of pure convection cooling for Rotating Detonation Combustors. Finally, the results are used to determine guidelines for the design of a cooled and efficient RDC.
Aerodynamics and Aeroacoustics of Leading Edge Serration in Low-Speed Axial Fans With Forward Skewed Blades
Authors: Tieghi Lorenzo , Czwielong Felix , Barnabei Valerio F. , Ocker Cristof , Delibra Giovanni , Becker Stefan , Corsini Alessandro
Published: September 2023

Low-speed axial fans must comply with a wide number of standards and normative restrictions, often related to the maximum noise emission levels. Among the noise control techniques in axial fans, skewed fan blades and leading edge (LE) serrations have been found to be effective in LE noise control, which represents one of the dominant phenomena in axial fan broadband emissions. However, these solutions are usually applied separately, and literture is scarce on systematic studies on the coupling of the two modifications. In this work, a campaign of experimental measurements was conducted on unskewed and forward-skewed axial fan blades with and without leading-edge serrtions. The tests were performed in undisturbed inflow conditions. The flow field and the turbulence characteristics were measured using 3D hot-wire anemometry. The suction-side sound radiation of the fans was measured with microphones in an anechoic chamber. In addition, the rotating beamforming method was used to localize the sound sources at the axial fans. It was found that, regardless of the blade skew, the leading edge serrations lead to a reduction of the sound pressure level, whereby the aerodynamic properties of the fan decrease. At the same operating points, which were achieved by adjusting the rotational speed, the sound radiation through the leading edge serrations could be reduced at high-volume flows. This effect was more pronounced with the unskewed rotor, which indicates that the positive effect of the serrations is reduced by the already optimized shape of the forward skewed fan blade. Based on the experimental results, the four geometries were further considered for numerical investigations to understand how the serrations affect the fan operations and the overall aerodynamics of the rotor. All four geometries were simulated with RANS approach at the duty point to derive a flow survey and better understand the dynamics driven by serrations and blade skewing.