bluuebunny/crossref_metadata_2025 huggingface dataset:
Unveiling the spatial distribution of aflatoxin B1 and plant defense metabolites in maize using AP‐SMALDI mass spectrometry imaging
Authors: Righetti Laura , Bhandari Dhaka Ram , Rolli Enrico , Tortorella Sara , Bruni Renato , Dall’Asta Chiara , Spengler Bernhard
Published: January 2021

In order to cope with the presence of unfavorable compounds, plants can biotransform xenobiotics, translocate both parent compounds and metabolites, and perform compartmentation and segregation at the cellular or tissue level. Such a scenario also applies to mycotoxins, fungal secondary metabolites with a pre‐eminent role in plant infection. In this work, we aimed to describe the effect of the interplay between Zea mays (maize) and aflatoxin B1 (AFB1) at the tissue and organ level. To address this challenge, we used atmospheric pressure scanning microprobe matrix‐assisted laser desorption/ionization mass spectrometry imaging (AP‐SMALDI MSI) to investigate the biotransformation, localization and subsequent effects of AFB1 on primary and secondary metabolism of healthy maize plants, both in situ and from a metabolomics standpoint. High spatial resolution (5 µm) provided fine localization of AFB1, which was located within the root intercellular spaces, and co‐localized with its phase‐I metabolite aflatoxin M2. We provided a parallel visualization of maize metabolic changes, induced in different organs and tissues by an accumulation of AFB1. According to our untargeted metabolomics investigation, anthocyanin biosynthesis and chlorophyll metabolism in roots are most affected. The biosynthesis of these metabolites appears to be inhibited by AFB1 accumulation. On the other hand, metabolites found in above‐ground organs suggest that the presence of AFB1 may also activate the biochemical response in the absence of an actual fungal infection; indeed, several plant secondary metabolites known for their antimicrobial or antioxidant activities were localized in the outer tissues, such as phenylpropanoids, benzoxazinoids, phytohormones and lipids.
A prospective multi‐faceted interventional study of blood bank technologist screening of red blood cell transfusion orders: The START study
Authors: Kron Amie T. , Collins Allison , Cserti‐Gazdewich Christine , Pendergrast Jacob , Webert Kathryn , Lieberman Lani , Zeller Michelle P. , Harding Sheila R. , Nahirniak Susan , Prokopchuk‐Gauk Oksana , Lin Yulia , Mendez Brent , Armali Chantal , Lee Christina , Watson Danielle , Arnott Dena , Xun Fengju , Blain Heather , Panchuk Heather , Hughes Hertha , Chorneyko Kathy , Angers Michael , Pilutti Nicole , Lett Ryan , Dowsley Shauna , Ruijs Theodora , Cupido Tracy , Kichinko Tracy , Thompson Troy , Afshar‐Ghotli Zohreh , Callum Jeannie ,   University of Toronto Quality in Utilization, Education and Safety in Transfusion (QUEST) Research Program
Published: January 2021

Background

Transfusion of red blood cells (RBC) is a common procedure, which when prescribed inappropriately can result in adverse patient outcomes. This study sought to determine the impact of a multi‐faceted intervention on unnecessary RBC transfusions at hospitals with a baseline appropriateness below 90%.

Study Design and Methods

A prospective medical chart audit of RBC transfusions was conducted across 15 hospitals. For each site, 10 RBCs per month transfused to inpatients were audited for a 5‐month pre‐ and 10‐month post‐intervention period, with each transfusion adjudicated for appropriateness based on pre‐set criteria. Hospitals with appropriateness rates below 90% underwent a 3‐month intervention which included: adoption of standardized RBC guidelines, staff education, and prospective transfusion order screening by blood bank technologists. Proportions of RBC transfusions adjudicated as appropriate and the total number of RBC units transfused per month in the pre‐ and post‐intervention period were examined.

Results

Over the 15‐month audit period, at the 13 hospital sites with a baseline appropriateness below 90%, 1950 patients were audited of which 81.2% were adjudicated as appropriate. Proportions of appropriateness and single‐unit orders increased from 73.5% to 85% and 46.2% to 68.2%, respectively from pre‐ to post‐intervention (P < .0001). Pre‐ and post‐transfusion hemoglobin levels and the total number of RBCs transfused decreased from baseline (P < .05). The median pre‐transfusion hemoglobin decreased from a baseline of 72.0 g/L to 69.0 g/L in the post‐intervention period (P < .0001). RBC transfusions per acute inpatient days decreased significantly in intervention hospitals, but not in control hospitals (P < .001). The intervention had no impact on patient length of stay, need for intensive care support, or in‐hospital mortality.

Conclusion

This multifaceted intervention demonstrated a marked improvement in RBC transfusion appropriateness and reduced overall RBC utilization without impacts on patient safety.
Rules of origin and consumer‐hurting free trade agreements*
Authors: Mukunoki Hiroshi , Okoshi Hirofumi
Published: January 2021

This study examines how the rules of origin (RoO) of a free trade agreement (FTA) affect firms' pricing strategies. The value‐added criterion (VAC) of the RoO requires firms to add more than a certain level of value within an FTA when firms use inputs originating from outside the FTA. The VAC may work as a price floor, and the resulting increases in prices can benefit all firms if it induces an offshoring firm to manipulate its output price. Meanwhile, a consumer‐hurting FTA formation is possible, even if all firms make tariff‐free exports. Furthermore, such an FTA formation may worsen total welfare.
Evaluation of prognostic impact of pre‐treatment neutrophil to lymphocyte and lymphocyte to monocyte ratios in dogs with oral malignant melanoma treated with surgery and adjuvantCSPG4‐antigen electrovaccination: an explorative study
Authors: Camerino Mariateresa , Giacobino Davide , Iussich Selina , Ala Ugo , Riccardo Federica , Cavallo Federica , Martano Marina , Morello Emanuela , Buracco Paolo
Published: January 2021

The role of systemic inflammation in cancer's progression has been widely investigated, especially in melanoma in humans. Pre‐treatment leukocyte counts and ratios play a recognized prognostic role in several types of malignancies, but no information is available regarding canine oral malignant melanoma (COMM). The purpose of this explorative retrospective study was to investigate the prognostic impact of pre‐treatment neutrophil to lymphocyte (NLR) and lymphocyte to monocyte (LMR) ratios in dogs with oral malignant melanoma that underwent surgical resection and immunotherapy with adjuvant CSPG4‐antigen electrovaccination. Thirty‐nine dogs with histologically confirmed oral melanoma and with available pre‐treatment haematological analyses, performed at maximum 60 days before the first treatment, were retrospectively enrolled. Statistical analysis was performed to explore possible correlations among NLR and LMR with age, clinical stage, tumour pigmentation, tumour size, nuclear atypia, mitotic index, Ki67, CSPG4 expression, ulceration, bone invasion and excision margins status. The impact of NLR and LMR on overall survival time (OST) was explored among various ratio cut off and across different time points with Kaplan‐Meier method. No significant relationship was identified between leukocytes ratios and histological parameters, CSPG4 expression, excision margin status, age, tumour size and clinical stage. NLR and LMR did not display a prognostic impact on the survival time of the entire population. Pre‐treatment leukocyte ratios may not represent a useful prognostic factor in dogs with oral melanoma, especially in absence of distant metastatic disease.
R1617Q epilepsy mutation slows NaV1.6 sodium channel inactivation and increases the persistent current and neuronal firing
Authors: Poulin Hugo , Chahine Mohamed
Published: January 2021

Key points

A human NaV1.6 construct was established to study the biophysical consequences of the R1617Q mutation on NaV1.6 identified in patients with unclassified epileptic encephalopathy and severe intellectual disability.

The R1617Q mutation disrupts the inactivation process of the channel, and more specifically, slows the current decay, increases the persistent sodium current that was blocked by tetrodotoxin and riluzole, and disrupts the inactivation voltage‐dependence and increases the kinetics of recovery.

In native hippocampal neurons, the R1617Q mutation exhibited a significant increase in action potentials triggered in response to stimulation and a significant increase in the number of neurons that exhibited spontaneous activity compared to neurons expressing WT channels that were inhibited by riluzole.

The abnormally persistent current activity caused by the disruption of the channel inactivation process in NaV1.6/R1617Q may result in epileptic encephalopathy in patients.

The voltage‐gated sodium channel NaV1.6 is the most abundantly expressed sodium channel isoform in the central nervous system. It plays a critical role in saltatory and continuous conduction. Although over 40 NaV1.6 mutations have been linked to epileptic encephalopathy, only a few have been functionally analysed. In the present study, we characterized a NaV1.6 mutation (R1617Q) identified in patients with epileptic encephalopathy and intellectual disability. R1617Q substitutes an arginine for a glutamine in the S4 segment of domain IV, which plays a major role in coupling the activation and inactivation of sodium channels. We used patch‐clamp to show that R1617Q is a gain‐of‐function mutation. It is typified by slower inactivation kinetics and a loss of inactivation of voltage‐dependence, which result in a 2.5‐fold increase in the window current. In addition, sodium currents exhibited an enhanced rate of recovery from inactivation, most likely due to the destabilization of the inactivation state. The alterations in the fast inactivation caused a significant increase in the persistent sodium current. Overexpression of R1617Q in rat hippocampal neurons resulted in an increase in action potential firing activity that was inhibited by riluzole, consistent with the gain‐of‐function observed. We conclude that the R1617Q mutation causes neuronal hyperexcitability and may result in epileptic encephalopathy.
The Thermal Behavior Analysis of a Human Eye Subjected to Laser Radiation Under the Non-Fourier Law of Heat Conduction
Authors: Alghamdi Najat A. , Youssef Hamdy M.
Published: January 2021

Purpose: The physiological conditions and environment have vital roles in the heat transfer in the human tissues, such as the multilayered human-eye. In this paper, a mathematical model of the human eye subjected to an exponential laser beam concerning the change in blood perfusion, porosity, evaporation rate, and ambient temperatures has been constructed based on non-Fourier heat conduction law. Methods: The human eye has been divided into six layers. Appropriate boundary and interface conditions have been considered. A separable function has been assumed, and the twelve equations have been formulated in matrix form. The solutions have been calculated by using maple 17 software. Results: The results have been shown in figures with different cases. The absolute temperature distribution based on various values of the power density of laser irradiation and relaxation times parameters have been discussed first. The effect of the blood perfusion, porosity, evaporation rate, time, and ambient temperatures have also been discussed. Conclusions: The power density of laser irradiation, blood perfusion, porosity, evaporation rate, time, and ambient temperatures significantly affects the value of the temperature passing through the human eye layers.
Design and Experimental Characterization of a Swirl-Stabilized Combustor for Low Calorific Value Gaseous Fuels
Authors: Dybe S. , Bluemner R. , Zhang K. , Schimek S. , Duwig C. , Stathopoulos P. , Paschereit C. O. , Bartlett M.
Published: January 2021

Low calorific value (LCV) gaseous fuels are generated as by-products in many commercial sectors, e.g., as mine gas or biogas. Their efficient exploitation can be a considerable source of primary energy. Typically, product gases from biomass are characterized by low lower heating values (LHVs) due to their high concentration of inert gases and steam. At the same time, their composition varies strongly based on the initial feedstock and may contain unwanted components in the form of tars and ammonia. These properties make the design of appropriate combustion systems very challenging and issues such as ignition, flame stability, emission control, and combustion efficiency must be accounted for. By employing a proprietary gas turbine burner at the TU Berlin, the combustion of an artificial LCV gas mixture at stoichiometric conditions has been successfully demonstrated for a broad range of steam content in the fuel. This work presents the stability maps and emissions measured with the swirl-stabilized burner at premixed conditions. It was shown that the flame location and shape primarily depend on the steam content of the LCV gas. The steam content in the fuel was increased until flame blow-out occurred at LHVs well below the target condition of 2.87 MJ/kg (2.7 MJ/mN3). The exhaust gas is analyzed in terms of the pollutants NOx and CO for different fuel compositions, moisture contents, and thermal powers. Finally, OH* measurements have been carried out in the flame. A simple reactor network simulation was used to confirm the feasibility of the experimental results.
Identification of Non-Transversal Motion Bifurcations of Linkages
Authors: Müller Andreas , López-Custodio P.C. , Dai J.S.
Published: January 2021

The local analysis is an established approach to the study of singularities and mobility of linkages. The key result of such analyses is a local picture of the finite motion through a configuration. This reveals the finite mobility at that point and the tangents to smooth motion curves. It does, however, not immediately allow to distinguish between motion branches that do not intersect transversally (which is a rather uncommon situation that has only recently been discussed in the literature). The mathematical framework for such a local analysis is the kinematic tangent cone. It is shown in this paper that the constructive definition of the kinematic tangent cone already involves all information necessary to distinguish different motion branches. A computational method is derived by amending the algorithmic framework reported in previous publications.
Design and Evaluation of Human–Machine Interface for NEXUS: A Custom Microassembly System
Authors: Wei Danming , Hall Mariah B. , Sherehiy Andriy , Popa Dan O.
Published: January 2021

Microassembly systems utilizing precision robotics have long been used for realizing three-dimensional microstructures such as microsystems and microrobots. Prior to assembly, microscale components are fabricated using micro-electromechanical-system (MEMS) technology. The microassembly system then directs a microgripper through a series of automated or human-controlled pick-and-place operations. In this paper, we describe a novel custom microassembly system, named NEXUS, that can be used to prototype MEMS microrobots. The NEXUS integrates multi-degrees-of-freedom (DOF) precision positioners, microscope computer vision, and microscale process tools such as a microgripper and vacuum tip. A semi-autonomous human–machine interface (HMI) was programmed to allow the operator to interact with the microassembly system. The NEXUS human–machine interface includes multiple functions, such as positioning, target detection, visual servoing, and inspection. The microassembly system's HMI was used by operators to assemble various three-dimensional microrobots such as the Solarpede, a novel light-powered stick-and-slip mobile microcrawler. Experimental results are reported in this paper to evaluate the system's semi-autonomous capabilities in terms of assembly rate and yield and compare them to purely teleoperated assembly performance. Results show that the semi-automated capabilities of the microassembly system's HMI offer a more consistent assembly rate of microrobot components and are less reliant on the operator's experience and skill.
Hydrodynamic Loads on Net Panels With Different Solidities
Authors: Føre Heidi Moe , Endresen Per Christian , Norvik Carina , Lader Pål
Published: January 2021

Drag forces on nets represent the largest contribution to hydrodynamic loads on traditional fish farms and will have a large impact on total loads on new designs utilizing netting as containment method. Precise methods for estimation of drag loads are needed. This article gives new knowledge on hydrodynamic forces acting on aquaculture nets. It presents results from towing tests, including updated drag and lift coefficients for Raschel-knitted netting materials used in nets for aquaculture, and quantify wake effect. The results include high solidity nets and high towing velocities. It was found that drag loads were close to proportional with the netting solidity for netting solidities ranging from 0.15 to 0.32. The wake effect is quantified through the average velocity reduction factor, which is given as a linear function of solidity. Much of the previously published data are close to the data found through these tests. However, for high solidity nets, the deviation is significant. Therefore, previously published data and models may overestimate drag loads for high solidity nets.
Incompatible Boundary Conditions in Heat Equation Coupled With Air System Models
Authors: Chaquet Jose M. , Corral Roque
Published: January 2021

Heat transfer problem is one of the main challenges in the design process of turbomachinery components for aeronautic applications. Good prediction capabilities are required to estimate metal temperatures, specially in those regions where the working fluid reaches temperatures near to the material melting point. In this context, it is common to perform multi-physics simulations involving different solvers. Special care must be taken at the interfaces between the several domains to avoid non-physical solutions. Concretely speaking, the coupling process between a thermal code (discretized heat diffusion equation solver) and a fluid network (low fidelity models representing air flows) is studied. Several non-physical boundary conditions examples are provided. The models are solved using an in-house thermal code called Saturn. The effects both in the results and in the convergence process are described. Non-physical boundary conditions provoke instabilities in the flow direction at some parts of the fluid network. A method to analyze the compatibility and convergence of the coupled problem is described and used in the examples. Also, some heuristics to achieve converge in the ill-posed models are commented.
Usage of Data Provenance Models in Collaborative Multi-Disciplinary Aero-Engine Design
Authors: Reitenbach S. , Vieweg M. , Hollmann C. , Becker R.-G.
Published: January 2021

The collaborative multi-disciplinary design of aircraft engines is a complex and highly iterative process. An essential characteristic of this design process is the involvement of a large number of experts from different disciplines, as well as the usage of numerous tools and workflows. Large amounts of data are produced and need to be exchanged via a multitude of interfaces. Furthermore, the data undergoes various transformations in the course of the design process. Understanding where a certain piece of data originates from and how it is connected to other datasets becomes therefore progressively essential. The purpose of this paper is to present a methodology to apply data provenance models in collaborative multi-disciplinary aero-engine design, supported by an approach for data standardization and identification. Besides the methodology, the software implementation to support this approach is presented in detail, including automated capturing and storage of provenance data, as well as methods for data investigation. In addition the presented methodology is evaluated by means of practical examples from the field of preliminary aero-engine design.
Obtaining Influence Coefficients in Different Formats With Reduced Number of Trial Runs on Two-Plane Balancing
Authors: Yu John J. , Péton Nicolas
Published: January 2021

Previously conversion equations of influence coefficients between multi-plane and static(in-phase)-couple(180 degrees out-of-phase) methods have been established. Sometimes one may have influence coefficients due to weight from one end only, but not both ends, plus those due to static or couple pair weight only but not both pairs. It has been found now that obtaining or knowing half of influence coefficients in the first method, plus half of those in the second method, can yield the other half of influence coefficients in both methods. In the other words, all influence coefficients in different formats can be obtained without a further trial run once one has half of influence coefficients in both methods. The above findings and conversion equations have been obtained analytically and verified by experimental results. A real application example is presented to demonstrate its efficiency in dealing with balancing tasks. The corresponding spreadsheets that can easily convert influence coefficients between different formats have been developed and used in real cases. Up to this point, all possible conversion equations of influence coefficients in different formats have been successfully discovered.
Heat Transfer and Flow Visualization of Equilaterally Staggered Jet Arrangement on a Flat Surface
Authors: Singh Alankrita , Prasad B. V. S. S. S.
Published: January 2021

The present study discusses two equilaterally staggered jet arrangements for uniform cooling of flat surface. The equilateral staggered arrangement consists of a circular jet surrounded by four neighboring chamfered jets at an angle of 45° called as chamfered configuration. An equilateral staggered jet arrangement consisting only of circular jets is considered as the non-chamfered configuration. Large-eddy simulations and Mie-scattering imaging techniques are discussed for heat transfer and flow visualization of equilateral staggered jet configurations. Formation of number of eddies characterizes the flow feature. The turbulence quantities of the jet configurations determine the amount of heat transfer. The eddies are formed due to recirculation which later breaks into smaller parts by the incoming jet fluid. The flow features basically constitute of jet to jet interaction, jet interference and upwash flow. It is also noticed that every jet cools an independent area. However with the inclusion of chamfered jets the region of highest heat transfer shifts away from the jet centerline. This happens because of change in direction of flow of jet due to chamfering. The heat transfer results are discussed in terms of Nusselt number and temperature contours. A maximum variation of 22.8% in average Nusselt number is obtained between both the configurations while varying the gap ratios between 3 to 7. An increase of jet-to-jet spacing ratio from 2 to 7 shows improvement in heat transfer by 15.1% and 13.2% for non-chamfered and chamfered configurations respectively.
Data Driven Fault Detection of Premixer Centerbody Degradation in a Swirl Combustor
Authors: Kumar Raghul Manosh , Peters Benjamin , Emerson Benjamin , Paynabar Kamran , Gebraeel Nagi , Lieuwen Timothy
Published: January 2021

This paper introduces a data-driven framework for combustor-focused, performance-based condition monitoring of gas turbines. Commercial condition monitoring systems typically generate huge amounts of data that make efficient onboard monitoring challenging. This paper focuses on quantifying combustor component degradation, using premixer centerbody degradation in a swirl stabilized combustor as a case study. The input for these analyses is acoustic pressure measurements acquired at various locations on the combustor. The diagnosis methodology is based on a classification framework and consists of 3 steps: 1) Data curation, 2) Feature Engineering, and 3) Diagnosis. Data curation ensures good quality of the data that is passed through the algorithm. Feature engineering deals with the extraction of the most informative features, from the most informative sensors, that can accurately capture the introduced fault. To perform diagnosis, the classification model is trained using experimentally acquired data and is then tested on a separate data set. The framework was able to achieve high classification accuracy (>99%) for training size as low as 30% of the total recorded observations. The low number of features required to achieve this accuracy suggests high potential for integration into existing onboard condition monitoring systems.
The Formation of High Temperature Minerals From an Evaporite-Rich Dust in Gas Turbine Engine Ingestion Tests
Authors: Elms Jacob , Pawley Alison , Bojdo Nicholas , Jones Merren , Clarkson Rory
Published: January 2021

The ingestion of multi-mineral dusts by gas turbine engines during routine operations is a significant problem for engine manufacturers because of the damage caused to engine components and their protective thermal barrier coatings. A complete understanding of the reactions forming these deposits is limited by a lack of knowledge of compositions of ingested dusts and unknown engine conditions. Test bed engines can be dosed with dusts of known composition under controlled operating conditions, but past engine tests have used standardised test dusts that do not resemble the composition of the background dust in the operating regions. A new evaporiterich test dust was developed and used in a full engine ingestion test, designed to simulate operation in regions with evaporiterich geology, such as Doha or Dubai. Analysis of the engine deposits showed that mineral fractionation was present in the cooler, upstream sections of the engine. In the hotter, downstream sections, deposits contained new, high temperature phases formed by reaction of minerals in the test dust. The mineral assemblages in these deposits are similar to those found from previous analysis of service returns. Segregation of anhydrite from other high temperature phases in a deposit sample taken from a High Pressure Turbine blade suggests a relationship between temperature and sulfur content. This study highlights the potential for manipulating deposit chemistry to mitigate the damage caused in the downstream sections of gas turbine engines. The results of this study also suggest that the concentration of ingested dust in the inlet air may not be a significant contributing factor to deposit chemistry.
Zonal Detached Eddy Simulation of the Fan-OGV Stage of a Modern Turbofan Engine
Authors: François Benjamin , Barrier Raphaël , Polacsek Cyril
Published: January 2021

The present article deals with the Zonal Detached Eddy Simulation of the fan module of a modern turbofan engine. The fan module, tested at the AneCom facility, is equipped with rotating fan blades and stationary outlet guide vanes (OGV). The simulation was performed to capture the interaction of the turbulent fan wakes with the OGV walls. The final goal of this simulation is the prediction of the associated broadband noise, not adressed here. In this paper, only the aerodynamic aspects are treated. The simulation relies on a hybrid RANS/LES approach with a zonal strategy: the core airflow is treated in RANS while the bypass airflow is solved with the hybrid approach. Mesh criteria meeting both RANS/LES and acoustic requirements were fulfilled, leading to a mesh of 380 million cells. The simulation was performed during five revolutions and statistical convergence was reached. Inspections of the flow-fields highlight a consistent behaviour of the shielding function (border between RANS and LES solving areas) around the blade walls, at the trailing-edge and in the tip gap flow areas. Comparisons with performance and hot-wire measurements are also presented. Aerodynamic performance and radial evolution of averaged velocities on a plane in-between the fan and the OGV are well retrieved, both in shape and levels. For the turbulent quantities, the shape of the radial profiles are close to the measurements, with much better accuracy in the upper region compared to the RANS solution.
Modal Velocity Perturbation Method for Contact Fatigue at Blade Attachment Under Resonant Vibration
Authors: Lamicq Olivier J. , Duong Loc Q.
Published: January 2021

In a gas turbine engine, it is often impossible to have rotating components running free of resonance at all operating conditions. As such, blades may be subject to episodes of intense vibration, resulting in fatigue damage at the connection between blade and disk. This paper presents a novel finite element approach allowing to evaluate in the time domain the behavior at the disk fir-tree or dovetail contacts caused by a high response on a resonance. The method can be applied to simple bending or torsion modes as well as to higher modes with complex shapes.

The application of a one-time velocity perturbation is an efficient way to initiate an oscillating motion at the frequency of interest. The behavior of the 3D-contact is then studied in the time domain, allowing non-linear behaviors to develop. The basic principle of this approach is described in this work.

In the design of turbomachinery blade attachments, this approach can be used to study in the time domain the fretting effect of load, coefficient of friction and sliding distance at different frequency regimes. In conjunction with fretting criteria such as Ruiz and Smith-Watson-Topper, fretting fatigue life can then be predicted.
Compressor Stall Warning Using Nonlinear Feature Extraction Algorithms
Authors: Lou Fangyuan , Key Nicole L.
Published: January 2021

Stall is a type of flow instability in compressors that sets the low-flow limit for compressor operation. During the past few decades, efforts to develop a reliable stall warning system have had limited success. This paper focuses on the small nonlinear disturbances prior to deep surge and introduces a new approach to identify these disturbances using nonlinear feature extraction algorithms including: phase-reconstruction of time-series signals and evaluation of a parameter called approximate entropy. To the best of the authors’ knowledge, this is the first time approximate entropy has been used for stall warning, and thus, its definition and utility are presented in detail. The technique is applied to stall data sets from two different compressors: a high-speed centrifugal compressor that unexpectedly entered rotating stall during a speed transient and a multi-stage axial compressor with both modal- and spike-type stall inception. In both cases, nonlinear disturbances appear, in terms of spikes in approximate entropy, prior to surge. The presence of these pre-surge spikes indicates the potential of using the approximate entropy parameter for small disturbance detection and stall warning. The details of the nonlinear feature extraction algorithm, including guidelines for its application as well as results from applying the algorithm to rig-level data, are presented.
Research on Optimization of the Design(Inverse) Issue of S2 Surface of Axial Compressor Based on Genetic Algorithm
Authors: Chen Zijing , Liu Bo , Wu Xiaoxiong
Published: January 2021

In order to further improve the effectiveness of design(inverse) issue of S2 surface of axial compressor, a design method of optimization model based on real-coded genetic algorithm is instructed, with a detailed description of some important points such as the population setting, the fitness function design and the implementation of genetic operator. The method mainly takes the pressure ratio, the circulation as the optimization variables, the total pressure ratio and the overall efficiency of the compressor as the constraint condition and the decreasing of the diffusion factor of the compressor as the optimization target. In addition, for the propose of controlling the peak value of some local data after the optimization, a local optimization strategy is proposed to make the method achieve better results. In the optimization, the streamline curvature method is used to perform the iterative calculation of the aerodynamic parameters of the S2 flow surface, and the polynomial fitting method is used to optimize the dimensionality of the variables.

The optimization result of a type of ten-stage axial compressor shows that the pressure ratio and circulation parameters have significant effect on the diffusion factor’s distribution, especially for the rotor pressure ratio. Through the optimization, the smoothness of the mass-average pressure ratio distribution curve of the rotors at all stages of the compressor is improved. The maximum diffusion factors in spanwise of rotor rows at the first, fifth and tenth stage of the compressor are reduced by 1.46%, 12.53% and 8.67%, respectively. Excluding the two calculation points at the root and tip of the blade because of the peak value, the average diffusion factors in spanwise are reduced by 1.28%, 3.46%, and 1.50%, respectively. For the two main constraints, the changes of the total pressure ratio and overall efficiency are less than 0.03% and 0.032%, respectively.

In the end, a 3-d CFD numerical result is given to testify the effects of the optimization, which shows that the loss in the compressor is decreased by the optimization algorithm.
Implementation of a Rig Test for Rotor/Stator Interaction of Low-Pressure Compressor Blades and Comparison of Experimental Results With Numerical Model
Authors: Pacyna Laura , Bertret Alexandre , Derclaye Alain , Papeleux Luc , Ponthot Jean-Philippe
Published: January 2021

To investigate the contact phenomenon between the blade tip and the abradable coated casing, a rig test was designed and built. This rig test fills the following constraints: simplification of the low-pressure compressor environment but realistic mechanical conditions, ability to test several designs in short time, at low cost and repeatability. The rig test gives the opportunity to investigate the behavior of different blade designs regarding the sought phenomenon, to refine and mature the phenomenon comprehension and to get data for the numerical tool validation.

The numerical tool considers a 3D finite elements model of low-pressure compressor blades with a surrounding rigid casing combined with a specialized model to take into account the effects of the wear of the abradable coating on the blade dynamics. Numerical results are in good agreement with tests in terms of: critical angular speed, blade dynamics and wear pattern on the abradable coated casing.
Analysis of the Losses in an Axial Fan With Small Blade Aspect Ratios Using CFD-Technique and Laser Doppler Anemometry
Authors: Theis Anika , Reviol Thomas , Böhle Martin
Published: January 2021

In this contribution an axial flow fan is designed with four different blade aspect ratios. These four blade aspect ratios are obtained by using four different numbers of blades. The blade aspect ratios are varied between 0.2 and 0.6. For this investigation the thickness ratio distribution and the spacing ratio are kept constant in the design process for all four blade aspect ratios. This means, the blade thickness, the spacing and the blade chord are adjusted for every blade aspect ratio. Analysing low aspect ratios is challenging. Previous literature treating compressors suggests that at low aspect ratio the secondary losses and the freestream losses combine, making it difficult to separate the profile loss from the secondary flow losses. An approach to quantifying profile losses at the midspan of the blades for blade aspect ratios lower than 0.5, 2D simulations at the midspan are carried out for supplementary examination. The Reynolds number of all investigations is related to the chord length of each blade. It is varied from 2.38 × 105 to 7.13 × 105. During the survey, the same stator with a constant blade aspect ratio as well as a constant spacing ratio is used.

In this contribution, LDA is applied as experimental method. Transient numerical simulations are performed for a full 3D simulation model to obtain a detailed view into the machine. Because of the low Reynolds numbers, the k-ω-SST transition model with the intermittency function is applied. With both methods, the flow is investigated on different planes inside the fan. The velocity distribution on the planes is analysed and compared to the transient simulation results. In the boundary layer, the velocity is resolved as well using the laser technique.
Section Based Profile Tolerance Assessment of 3D Scanned Compressor Airfoils
Authors: Lange Alexander , Johnson Dean , Key Nicole
Published: January 2021

This paper presents two turbomachinery-specific methods for profile tolerance assessment of compressor airfoils that process 3D scan data. This optical inspection technology digitizes the entire surface of the part into a triangulated mesh, which is aligned to nominal geometry and then processed to extract densely arranged profile sections.

For the reverse engineering method, the profile sections are decomposed into thickness and camber distributions. These distributions and the camber line are used to identify the profile parameter vector of the reverse engineering model. The deviation of the actual geometry is obtained by subtracting its parameters from those of the nominal geometry. Parameter-span graphs reveal airfoil shape deviation and allow for quantification of blisk scatter. The design-like parameters are meaningful and enable an intuitive engineering judgement of the actual geometry deviation.

The profile tolerance assessment method utilizes the camber line from the reverse engineering method to elegantly check against variable profile tolerance limits. The actual section is best-fitted to its nominal counterpart and assessed regarding its deviation relative to the allowed local tolerance. This ratio is plotted in a developed view summarizing the result of the profile tolerance assessment for the whole airfoil in a single graph. Thus, the condensed results allow for effective utilization of the high-resolution in airfoil sections.

Ultimately, the paper widens the view from one airfoil towards the assessment of the entire blisk. The blisk data is presented by statistical processing of deviation fields of all airfoils, in terms of mean and standard deviation. These statistical quantities are plotted onto the airfoil contour to e.g. represent the average airfoil thickness of the blisk. The standard deviation plot points to airfoil sections of larger geometric scatter and reveals areas of a non-robust manufacturing process.
Study on Accuracy of Heat Transfer Coefficient Determination in the Bearing Chamber for Gas Turbine Engine
Authors: Petukhov Illia , Mykhailenko Taras , Yepifanov Sergiy , Shevchuk Oleg
Published: January 2021

The heat transfer coefficient (HTC) is one of the key parameters that should be known at the stage of the bearing chamber design. This ensures safe temperature conditions for the lubrication oil and reliable operation of the gas turbine engine. The temperature gradient method is commonly used in experimental practice to determinate the HTC. The accuracy of the HTC determination is sensitive to changing of the bearing chamber operating conditions and should be analyzed at the stage of experimental studies planning. This paper presents a study on the accuracy of HTC determination when the external cooling of the bearing chamber is used to obtain the temperature difference sufficient for measurement. Three ways to reduce the relative error of the HTC determination in the bearing chamber were analyzed: i) decreasing the temperature measurement error; ii) decreasing the temperature of external cooling medium; iii) increasing the external heat transfer coefficient and contribution of wall thermal resistance optimization. For different operating conditions of the bearing chamber, the temperature of the outer wall that ensures the specified accuracy of the experimental HTC and the required parameters of the cooling medium were determined and recommended for practical implementation.
Aerodynamic Loading Considerations of Three-Shaft Engine Compression System During Surge
Authors: Moreno Jose , Dodds John , Sheaf Christopher , Zhao Fanzhou , Vahdati Mehdi
Published: January 2021

Compressor surge imposes a limit on aero-engine operability and can compromise integrity because of significant aerodynamic loads imparted on the engine components. The aim of this paper is to use 3D unsteady CFD to predict the surge loadings on a modern three spool engine. The computations are performed using a whole-assembly approach. In this work, the effect of two types of surge initiation on the maximum loading recorded during surge are studied and a physical explanation of the main phenomena which contribute to those loadings is offered. The engine is matched at a high power condition and the surge inception is via throttling of the high pressure compressor (HPC) or turning of the intermediate pressure compressor (IPC) variable stator vanes. It was found that in an aero-engine surge event, the maximum overpressure are caused by a combined effect of the surge shock wave passing and high pressure gas blown towards the front of the engine during depressurisation. The overpressure is dictated by the compression system exit pressure at the moment of the surge inception. The surge initiation via HPC throttling produces larger overpressure and therefore, should be considered for design considerations.
Investigation Into the Effects of Hub Rotation on the Hub Leakage Flow of Cantilever Stator in a Transonic Axial Compressor
Authors: Zhang Botao , Liu Bo , Sun Xin , Zhao Hang
Published: January 2021

In order to explore the similarities and differences between the flow fields of cantilever stator and idealized compressor cascade with tip clearance, and to extend the cascade leakage model to compressors, the influence of stator hub rotation to represent cascade and cantilever stator on hub leakage flow was numerically studied. On this basis, the control strategy and mechanism of blade root suction were discussed.

The results show that there is no obvious influence on stall margin of the compressor whether the stator hub is rotating or stationary. For rotating stator hub, the overall efficiency is decreased while the total pressure ratio is increased. At peak efficiency point and near stall point, the efficiency is reduced by about 0.43% and 0.34% individually, while the total pressure ratio is enlarged by about 0.23% and 0.27%, respectively.

The gap leakage flow is promoted due to stator hub rotation, and the structure of the leakage vortex is weakened obviously. In addition, the hub leakage flow originating from the blade leading edge of rotating hub may contribute to double leakage near the trailing edge of the adjacent blade. However, the leakage flow directly out of the blade passage with stationary stator hub. The stator root loading and strength of the leakage flow increase with the rotation of the hub, and the leakage vortex is further away from the suction surface of the blade and is stretched to an ellipse closer to the endwall under the shear action. The rotating hub makes the flow loss near the stator gap increase, while the flow loss in the upper part of the blade root is decreased. Meanwhile, the total pressure ratio in the end area is increased.

Blade root suction of cantilever stator can effectively control the hub leakage flow, inhibit the development of hub leakage vortex, and improve the flow capacity of the passage, thereby reducing the flow loss and modifying the flow field in the end zone.
Investigations Into Aerodynamic Performance of Turbine Stages With Flexible Shroud Seals
Authors: Yan Xin , Wang Yabo , Zhang Kang , Dai Xinbo , He Kun
Published: January 2021

The present paper utilizes a numerical method to investigate the effect of flexible shroud seals, including the forward bending flexible seals and backward bending flexible seals, on aerodynamic performance of high pressure steam turbine stages. At first, the wear performance of flexible seal is analyzed with the Finite Element Analysis method. It shows that wear in flexible strip is so small that only the installation clearance needs to be considered in operation process. Then, by replacing the labyrinth shroud seals with flexible shroud seals, the aerodynamic efficiency, outlet flow angle distributions, and reaction degree distributions in two-stages are obtained. At three installation clearances, interactions between leakage flow and main flow, as well as the flow patterns in flexible shroud seals, are visualized and also compared with the original design case. The numerical results indicate that turbine stages configured with forward bending flexible shroud seals have a very close aerodynamic performance to those configured with conventional labyrinth shroud seals at the same clearance, whereas the turbine stages configured with backward bending flexible seals have lower total-total isentropic efficiency than those with conventional labyrinth shroud seals. By replacing the conventional labyrinth shroud seals with forward bending flexible shroud seals (at the same clearance), the aerodynamic efficiency, outlet flow angles, limiting streamlines, secondary flow patterns in shroud region and reaction degree distributions in stages are almost not affected. Since the forward bending flexible seal allows relatively smaller installation clearance than the conventional labyrinth seal, application of this kind of seal in rotor blade tip gap is much beneficial to achieve lower leakage rate and higher aerodynamic performance in large power steam turbine stages.
Investigation on Mixing Characteristics of Methane Fuel in Low Emission Combustor
Authors: Liu Enhui , Liu Xiao , Zheng Hongtao , Lu Jinghe , Zhang Zhihao , You Binchuan
Published: January 2021

With the increasingly environmental problems and strict pollutant emission limits, pollutant emission has become a critical consideration for gas turbine. Mixing uniformity index of fuel-air has a significant effect on NOx emission. Previous works conducted basic research on mixing mechanism based on jet in crossflow, while few people studied a single real swirler channel in gas turbine combustor. The present work aims to bridge this gap and investigates the effects of fuel injection from the windward and leeward sides on the fuel concentration distribution and mixing uniformity index, based on a typical radical swirler channel. The qualitative analysis of velocity field and vortices structure and the quantitative analysis of velocity ratio and uniformity index are carried out. Due to the presence of sharp corner at the inlet of swirler, a recirculation zone is formed by the flow separation. The recirculation zone at the leeward side decreases the flow velocity and increases the area and time for fuel-air mixing. The velocity ratio plays a key role in the characteristics of flow and mixing. Under the same inlet conditions, the effective velocity ratio (R = 40) in the near field of the leeward side is about 10 times that of windward side (R = 4), and the maximum jet depth can be achieved in the near field. Therefore, the outlet uniformity index on the windward and leeward sides are 38.85% and 49.43%, respectively. From the perspective of mixing uniformity, fuel injection from the leeward side is beneficial to realize quick mixing in short distance. The present study is expected to provide insightful information for understanding mixing characteristics of methane fuel in low emission combustor.