bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of broiler plasma metabolic spectrum by the addition of lysine residue to the diet
Authors: Zhang Juan , Wang Weizhen , Wang Ying , Hu Honghong , Yu Baojun , Zhou Zihang , Guo Ju , Gu Yaling , Cai Zhengyun , Xin Guosheng
Published: September 2021

Flavour is an important factor in evaluating meat quality, and amino acids and fats are important components affecting meat flavour. In this study, we evaluated the relationship between the variation of lysine residue addition and the slaughter performance and meat quality of broilers, which decreased with the addition of lysine residues but improved the meat quality of the broilers. 10% lysine residue addition was the most beneficial for reducing feed cost and improving meat quality. Meanwhile, the plasma metabolites of broilers fed increasing concentrations of lysine residue supplemented feeds were analysed using liquid chromatography‐mass spectrometry (LC‐MS). Principal component analysis (PCA) and partial least square discriminant analysis (OPLS‐DA) were used screen, the differential metabolites induced by lysine residue. In the broilers 29, 37, 63, 87, 80 and 111 differential metabolites were detected (p < 0.05). Amongst them, 3‐iodotyrosine, N‐methyl‐L‐glutamic acid, coumaraldehyde, 2‐dimethylphenol, N‐methylnicotinamide and L‐erythrone were the common differential metabolites between group A and groups B, C, D, E, F and G. The addition of lysine residue was positively correlated with alanine aminotransferase (p < 0.05, r = 0.942) and high‐density lipoprotein cholesterol (p < 0.05, r = 0.798) and negatively correlated with aspartate aminotransferase (p < 0.05, r = 0.822). According to the classification of differential metabolites and their enriched pathway analysis, differential metabolites mainly caused changes in amino acid and lipid metabolism. Our study shows that a certain proportion of lysine residue in diet affects the specific metabolic pathway of broilers, which may affect amino acid and fat metabolism by regulating alanine aminotransferase, aspartate aminotransferase and high‐density lipoprotein cholesterol, ultimately affecting the flavour.
Mothers' perceptions of self‐efficacy and satisfaction with parenting are related to their use of controlling and positive food parenting practices
Authors: Holley Clare E. , Haycraft Emma
Published: September 2021

Perceptions of parenting competence are composed of self‐efficacy and satisfaction with parenting. Parenting competence is linked to differential outcomes across numerous parenting domains. To date, few studies have explored the relationships between maternal self‐efficacy and food parenting practices, deploying different measures and age ranges, and yielding conflicting findings. Therefore, the current study sought to explore relationships between the two dimensions of perceived parenting competence and the use of controlling and positive food parenting practices. UK mothers (N = 269) of 18‐ to 59‐month‐old children completed measures of both dimensions of perceived parenting competence (i.e., parenting self‐efficacy and satisfaction) and of controlling (maladaptive) and positive (health promoting) food parenting practices. Relationships were found between perceptions of competence and use of food parenting practices. Self‐efficacy and satisfaction with parenting were positively associated with the use of most positive food parenting practices. Greater parenting satisfaction, but not parenting efficacy, was associated with lower use of some of the potentially detrimental controlling food parenting practices. Neither parenting self‐efficacy nor satisfaction with parenting were related to mothers' reported use of pressure to eat. In conclusion, supporting and promoting greater maternal self‐efficacy and satisfaction with parenting may be a useful target for public health interventions and for professionals working with families with the aim of promoting optimal parenting to support children's development of healthy eating habits. Future research should seek to further elucidate the current findings with a longitudinal design.
The transition of labour in the presence of adaptation cost and labour market segmentation
Authors: Mahanta Amarjyoti
Published: September 2021

In this paper, we explore the process of transition of labourers from the traditional to the modern sector. The firms in the modern sector can initially differentiate between migrant workers and native workers. However, as the number of workers from the traditional sector increases, the firm cannot segment the labour market. The migrants bear an adaptation cost. The process of transition of labour (migration) is studied through the replicator map. We study the nature of migration in the long run. When adaptation cost monotonically decreases in the share of labourers from the traditional sector engaged in the modern sector, we get an unstable interior equilibrium and two stable equilibria at the boundary. We show convergence to the stable fixed points. When the adaptation cost is non‐monotonic, we get four equilibrium points of which two are stable and two unstable. We get a stable interior equilibrium point implying that only a fraction of labourers is going to shift to the modern sector in the long run. We also show convergence to the stable fixed points under certain conditions on the derivative of the difference equation.
ANU productions and the performance of otherness
Authors: Singleton Brian
Published: September 2021

Taking my lead from Ric Knowles’s analysis of interculturalism 'from below’ (Knowles, 2017, 2), the focus of this essay is on the representation of ‘otherness’ in three productions of Ireland’s multi‐award‐winning company ANU Productions: their 2014 play Vardo about ‘travellers’ in an inner‐city community; their 2016 play Sunder, in which contemporary Chinese characters were placed in a centenary production about Ireland’s failed revolution; and in their 2019 production, Faultline, where a previously unknown Black British singer emerges from the Irish Queer Archive. ANU Productions’ intercultural strategy contests monocultural constructions of Ireland, by throwing spectators, without exposition, into often historical scenes featuring characters from other worlds, nations, races and ethnicities. These characters, by their very visual and aural presence in performances ostensibly of monocultural historical experiences, refract and at times challenge essentialist tendencies to write histories of nation. ANU’s focus has always been on ‘others’, the bystanders to history, on those absent from historical constructions. But in their folding of the present into the performed past, a folding the company calls ‘NOW THEN NOW’, new ‘others’ emerge as bystanders, inviting us to stand by them as well.
Postoperative pharmacotherapy for patients with biliary atresia in Japan
Authors: Sakamoto Saki , Hashizume Naoki , Yagi Minoru , Sasaki Hideyuki , Nio Masaki ,   The Japanese Biliary Atresia Society
Published: September 2021

Background

Members of the Japanese Biliary Atresia Society were surveyed using questionnaires that assess their current practice regarding postoperative pharmacotherapy for outpatients with biliary atresia (BA).

Methods

In September 2018, questionnaires were sent to 100 member institutions of the Japanese Biliary Atresia Society. Questionnaires included the number of BA outpatients per institution and pharmacotherapy for outpatients with native liver. Pharmacotherapies were categorized into antibiotics, cholagogues, hepatoprotective agents, branched‐chain amino acid supplement, Japanese Kampo medicine, probiotics, laxative, glycerin enema, and “others.” In each category, the questionnaires asked about the medicine's details and the time of withdrawal of administration.

Results

Responses were collected from 58 of the 100 institutions. Fifty‐four institutions (94.7%) had prescribed one or more medicines as postoperative pharmacotherapy, and three institutions (5.3%) did not prescribe any medicines. Fifty‐three institutions (93.0%) had prescribed ursodeoxycholic acid (UDCA), and 32 (60.4%) of these continued prescribing UDCA as long as the condition of patients remained unchanged. Twenty‐nine (50.9%) had prescribed Japanese Kampo medicines (“Inchinkoto” in all cases). Twenty‐four (42.1%) had prescribed antibiotics, mainly trimethoprim‐sulfamethoxazole, in 21 (87.5%). Twenty‐three (40.4%) had prescribed probiotics.

Conclusions

There were many variations of pharmacotherapy in BA outpatients with native liver in Japan, including antibiotic, probiotic, and Inchinkoto prescriptions. Of the various drugs, the most commonly administered was UDCA.
TB in paediatric kidney transplant recipients – A single‐centre experience
Authors: Makanda‐Charambira Privilage D. , Nourse Peter , Luyckx Valerie A. , Coetzee Ashton , McCulloch Mignon I.
Published: September 2021

Background

TB remains a major challenge in transplantation, particularly in endemic countries. This study aimed to describe the incidence, clinical presentation and outcomes of TB in paediatric kidney transplant recipients and to assess the impact of INH prophylaxis.

Methods

Single‐centre retrospective descriptive analysis of children who received kidney transplants from 1995 to 2019 was carried out. The cohort was stratified according to receipt of INH prophylaxis which began in 2005.

Results

A total of 212 children received a kidney transplant during the study period. Median age at transplantation was 11.2 years (IQR: 2.2–17.9), and 56% were males. TB was diagnosed in 20 (9%) children, with almost two‐thirds (n = 12) occurring within the first year. Most infections were pulmonary. The main presenting symptoms included fever (n = 13/20), weight loss (n = 12/20) and cough (n = 10/20). TST was positive in four of 20 children. Coinfection with EBV, CMV or Staph was found in five children. Due to drug interactions, an up to threefold increase in calcineurin inhibitor dose was required to maintain therapeutic blood levels. INH prophylaxis was protective against development of TB (p = .04). Gender, age and type of allograft were not significant risk factors. Graft and patient survival was 100% upon completion of TB treatment.

Conclusion

Kidney transplant recipients in endemic countries have a high risk of developing TB. Diagnosis remains a challenge. Frequent and meticulous monitoring of immunosuppression drug levels during treatment of TB is required to avoid loss of patient or graft. INH prophylaxis protects against development of TB in this population.
What drives life insurance purchasing decisions in Bosnia and Herzegovina?
Authors: Kozarevic Safet , Hodzic Sanida
Published: September 2021

Life insurance has become increasingly relevant in Bosnia and Herzegovina (BiH) over the last 10 years. The market is still underdeveloped with low life insurance density (EUR 23.2 per capita in 2019), however, it shows great potential with growth rates averaging 8.7%. The examination of the drivers of life insurance demand should instruct life insurers and policymakers to implement strategies to accelerate the life insurance development in BiH. Life insurance purchasing decisions are influenced by series of determinants, reflecting the customers' experiences and preferences. The purpose of this paper is to examine the determinants of customer life insurance purchasing decisions. We consider the following factors: Income, insurance policy price, propensity to save, insurance policy yield, product‐offer, corporate image, and brand. The research covers the existing and potential customers in BiH. Two hundred respondents participated in a survey who were selected according to different sociodemographic characteristics. The main findings show the relevance of particular determinants and their differences that can be helpful for insurance companies in creating their strategy for market growth.
Count‐ versus MAD‐based accelerometry‐assessed movement behaviors and associations with child adiposity and fitness
Authors: Verswijveren Simone J. J. M. , Douglas Benjamin , Rantalainen Timo , Belavy Daniel L. , Salmon Jo , Timperio Anna , Lubans David R. , Ridgers Nicola D.
Published: September 2021

Estimations of time spent sedentary and in various physical activity intensities may vary according to data reduction methods applied. This study compared associations between children's accelerometer data and adiposity and fitness markers using open source (mean amplitude deviation, MAD) and proprietary (counts) data reduction methods. Complete‐case accelerometer, adiposity (Body Mass Index z‐score, waist circumference), and fitness (cardiorespiratory, musculoskeletal) data from 118 children (10.4 ± 0.6 years, 49% girls) were analyzed. Estimates of sedentary behavior, light‐, moderate‐, vigorous‐ (VPA), and moderate‐ to vigorous‐intensity (MVPA) physical activity were calculated using count‐ and MAD‐based data reduction methods. Linear regression models between time in movement behaviours and fitness and adiposity markers were conducted. Significant differences in estimates of time spent in all intensities were observed between MAD‐based and count‐based methods. Both methods produced evidence to suggest that sedentary behavior was detrimentally, and physical activity (any intensity) was beneficially, associated with waist circumference. MVPA and VPA were beneficially associated with fitness markers using both data reduction measures. Overall, findings suggest that estimates of sedentary time and physical activity were not comparable. However, the strength and direction of the associations obtained between the different data reduction methods and adiposity and fitness outcomes were fairly comparable, with both methods finding stronger associations for VPA compared to MVPA. This suggests that future studies may be able to pool data using different data reduction approaches when examining associations between activity and health risk factors, albeit with caution.
Exploring the impact of COVID‐19 on mobile dating: Critical avenues for research
Authors: Gibson Alexandra Farren
Published: September 2021

In this digitally mediated world, initiating sexual or romantic intimacy now frequently occurs on mobile dating apps, which both requires people to navigate new technologies, but also enables them to explore different possibilities for intimacy. The opportunities that mobile dating holds for creating intimacy, and how people take these up, is particularly relevant in light of the global pandemic of COVID‐19, when human connection and contact are entangled with varying worries about viral contamination, risk and future uncertainty. But how does the pandemic impact on mobile dating? How are affect and risk intertwined—or even negotiated—by people in their search for intimacy in this pandemic? What possibilities do mobile dating apps hold for people in their search for connection with others? In this commentary, I provide a brief overview of how risk has been examined previously in mobile dating research and explore what future directions could be taken in this field. I argue for research that acknowledges and prioritises: the plurality of people's sociomaterial conditions; the interrelationship between people, digital technologies and COVID‐19; and the discursive context that furnishes people's sense of risk and emotional possibility across different sociocultural contexts. These new directions in the field offer opportunities to conduct critical research that is responsive to this dynamic context, and that illuminates the various ways that people are navigating intimacy, risk and emotion across different living conditions during this pandemic.
Study on Transfer Matrix Method for the Planar Multibody System With Closed-Loops
Authors: Zhang L. N. , Rui X. T. , Zhang J. S. , Gu J. J. , Zheng H. Q. , Li T.
Published: September 2021

The conventional transfer matrix method for multibody systems (MSTMM) with closed-loops (CLs) has superiority of avoiding the global dynamics equations. However, it requires a transfer equation to link multiple-input single-output (MISO) rigid body with multihinge subset and supplement equations caused CLs. In order to simplify the deduction processing and improve the numerical stability, the Riccati transformation is introduced and the Riccati transfer matrix method for multibody systems (RMSTMM) with CLs is proposed. In a system with CLs, each CL is cut off at the connection point, and the new unknowns generated at the cutoff point are introduced into the Riccati recurrence relation. The numerical results of the conventional MSTMM and the RMSTMM are compared, and the reliability of the RMSTMM is verified. Meanwhile, the constrained Jacobian matrix is used to eliminate the constraint violation of the system. The variations of the constraint violation error are compared to validate necessarily of constraints.
Robust Co-Design: Coupling Morphology and Feedback Design Through Stochastic Programming
Authors: Bravo-Palacios Gabriel , Grandesso Gianluigi , Prete Andrea Del , Wensing Patrick M.
Published: September 2021

This article proposes a new framework for the computational design of robots that are robust to disturbances. The framework combines trajectory optimization (TO) and feedback control design to produce robots with improved performance under perturbations by co-optimizing a nominal trajectory alongside a feedback policy and the system morphology. Stochastic programming (SP) methods are used to address these perturbations via uncertainty models in the problem specification, resulting in motions that are easier to stabilize via feedback. Two robotic systems serve to demonstrate the potential of the method: a planar manipulator and a jumping monopod robot. The co-optimized robots achieve higher performance compared to state-of-the-art solutions where the feedback controller is designed separately from the physical system. Specifically, the co-designed controllers show higher tracking accuracy and improved energy efficiency (e.g., 91% decrease in tracking error and ≈5% decrease in energy consumption for a manipulator) compared to linear quadratic regulator applied to a design optimized for nominal conditions.
On the Design of an ORC Axial Turbine Based Expander Working As a Mechanical Driver in Gas Compressor Stations
Authors: Branchini Lisa , Celis Cesar , Ruiz Sebastian , Aguilar Rene , De Pascale Andrea , Melino Francesco
Published: September 2021

In this work, the feasibility of increasing the capacity of a natural gas compressor station by means of an Organic Rankine Cycle (ORC) is studied. In the proposed configuration, the ORC recovers natural gas compressor drivers’ wasted heat and converts it into mechanical energy. Thus, as innovative approach, the ORC generated mechanical power will be used to drag an additional gas compressor. A case study representative of a medium-size on-shore facility is taken as reference. The mechanical drivers’ arrangement is composed of four recuperated GTs of PGT5 R type (three units continuously operating and one used as back-up) and two smaller engines of Solar Saturn 20 type. Assuming the actual operation of the station, the addition of an ORC, as bottomer cycle, is designed to recover the exhaust heat from the three PGT5 R running units. According to the Authors’ preliminary investigations and state of the art MW-size parameters, a regenerative sub-critical ORC cycle is selected. Therminol 66 and Hexamethyldisiloxane (MM) are chosen as intermediate and working fluids, respectively. The design ORC key cycle parameters are identified: about 2700 hp (2 MW) of capacity could be added to drive a compressor. For a comprehensive investigation, ORC off-design operating range is explored too assuming one out of three topper cycle units out of service. Since a direct coupling of the ORC driver and the gas compressor is expected, thus excluding the use of gearboxes to avoid losses, an ORC axial turbine based expander is designed that accommodates variable speed operation. The referred design includes mean-line calculations and three-dimensional computational fluid dynamics (CFD) based numerical simulations at design and off design point conditions.
Development of Loss Correlation and Tool Validation at Transonic Condition Based on Cascade Test
Authors: Choi Jaewoo , Simurda David , Song Jaewook , Luxa Martin , Lee Sungryong , Hala Jindrich , Lepicovsky Jan , Radnic Tomas , Seo Junhyuk
Published: September 2021

Overall efficiency of an axial compressor is largely affected by its front stage when it is operating under transonic flow conditions. For this reason, many manufacturers and researchers are advancing research and development of transonic airfoils in these days. Doosan, in frame of a development of high efficiency gas turbine, developed high efficiency airfoil for a transonic rotor and conducted cascade tests. Therefore, this study deals with a test of two compressor transonic blade cascades at inlet Mach number over 1.1. To improve the efficiency and operating range, two kinds of thickness distribution type based on Enhanced Doosan Airfoil (EDA), which applied unique rule, were applied and assessed. The first airfoil consists of polynomial thickness distribution and the second airfoil consists of new thickness distribution with specially tailored leading edge. In order to ensure accurate geometry of a model, a detailed checkout process upon production of model blades used in the test was performed. This is because, in the case of transonic airfoil, if the inlet leading edge shape differs by more than 0.2% than designed airfoil of leading edge, the result will be completely different. Therefore, not only the tolerance within 0.1% was confirmed but also the shape produced through simulation and 3D CMM scan data. The main parameters for the comparison are an inlet Mach number, an axial velocity density ratio (AVDR) and the kind of thickness distribution. Results of tests and CFD blade to blade analysis using MISES 2.70 are compared. The flow field was visualized using schlieren technique and parameters of the suction side boundary layer were evaluated at several locations based on Pitot probe traverses. The results confirm that a suction peak at the round leading edge disappears in the case of the new thickness type distribution with tailored leading edge. This confirms that the profile shaping without jump in curvature in the leading edge region leads to smooth acceleration without peaks. Nevertheless, results show that the new thickness distribution type is not absolutely good in comparison with the polynomial thickness distribution type with respect to the total pressure loss coefficient. Moreover, bucket range (operating range) is also almost the same. Results of the suction side boundary layer traversing suggest that the transition of the boundary layer takes place beyond the location x/cax > 0.088. The MISES results show that a shock location and the boundary layer parameters are similar to test results. However, values of the loss coefficient show some difference. Therefore, a new correlation in particular transonic flow condition was developed.
An Update on the Status of a Reduced Flow Test of a 10mw 700°C sCO2 Integrally Geared Compander
Authors: Katcher Kelsi M. , Wilkes Jason , Allison Tim C.
Published: September 2021

In order to maintain viability as a future power-generating technology, concentrating solar power (CSP) must reduce its levelized cost of electricity (LCOE). One component of solving this problem is reducing the cost of the power block while simultaneously increasing the efficiency of the thermodynamic cycle. One disruptive technology that has the promise to accomplish this is supercritical CO2 based power cycles. These cycles are conceptually similar to steam cycles; however, they have substantially smaller turbomachinery at equivalent power while also delivering more efficiency at turbine inlet temperatures of 500–700°C. This paper will summarize the current status of a US Department of Energy project to develop machinery to support a 10 MW sCO2 power cycle. The team of Southwest Research Institute® (SwRI®) and Hanwha Power Systems America, proposed to develop an integrally-geared (IG) compressor-expander (compander) for use in a nominal 10 MW-scale CSP supercritical carbon dioxide (sCO2) plant application. This integrally-geared compander (IGC) comprises multiple pinion shafts interconnected on a single bull gear to create a compact package, and utilizes a low-cost, low-speed driver. In addition, the integrally-geared architecture allows each pinion to operate at different rotational speeds to optimize performance and easily allow for inter-stage cooling and turbine re-heat to further enhance both stage and cycle efficiency. The close integration of all turbomachinery elements into a single integrally-geared (IG) machine creates a design that lends itself to power block modularization, which makes it suitable for waste heat recovery, fossil fuel power plants, and especially CSP applications. As part of the commercialization of this technology, it is necessary to reduce risk by validation testing of key components. In the current work, the focus is developing a test loop to enable safe testing of the main compressor stage across a wide range of operating conditions, and to validate the mechanical integrity of the turbine at full pressure, temperature, and speed. Developing a test loop for sCO2 requires balancing a number of design alternatives that impact cost, lead time, safety, and performance. The current work discusses the design process for the reduced flow test loop for the compander.
Matrix Crack Networks in SiC/SiC Composites: In-Situ Characterisation and Metrics
Authors: Jordan S. P. , Jeffs S. P. , Newton C. D. , Gale L. , Nicholson P. I. , Bache M. R.
Published: September 2021

Ceramic matrix composites can offer clear potential for a variety of engineering applications where the temperature capabilities of conventional metals are exceeded. Continued mechanical characterisation is essential to gain an understanding of their associated damage and failure mechanisms across a wide range of representative temperatures. The present paper will report ongoing research to characterize the initiation of matrix cracking at room temperature under tensile stress and subsequent damage development under fatigue loading in a SiCf/SiC composite. Imaging and mechanical property data were obtained via in-situ loading within a scanning electron microscope. The temporal nature of damage development was also recorded through the selective employment of acoustic emission. Metrics to describe the spatial distribution of cracks, crack lengths and crack opening displacement under load will be presented. The inspections also provided detailed evidence of the associated crack closure phenomena. The understanding of matrix crack saturation and matrix/fibre interfacial mechanics will be explored, together with the implications for the use of X-ray tomographic inspection of engineering components during service. The potential for these emergent techniques as a basis for future CMC characterization, via automated image recognition and machine learning, will be highlighted.
Calculation of Nonlinear Systems Under Narrow Band Excitation Using Equivalent Linearization and Path Continuation
Authors: Förster Alwin , Panning-von Scheidt Lars
Published: September 2021

Turbomachines experience a wide range of different types of excitation during operation. On the structural mechanics side, periodic or even harmonic excitations are usually assumed. For this type of excitation there are a variety of methods, both for linear and nonlinear systems. Stochastic excitation, whether in the form of Gaussian white noise or narrow band excitation, is rarely considered. As in the deterministic case, the calculations of the vibrational behavior due to stochastic excitations are even more complicated by nonlinearities, which can either be unintentionally present in the system or can be used intentionally for vibration mitigation. Regardless the origin of the nonlinearity, there are some methods in the literature, which are suitable for the calculation of the vibration response of nonlinear systems under random excitation. In this paper, the method of equivalent linearization is used to determine a linear equivalent system, whose response can be calculated instead of the one of the nonlinear system. The method is applied to different multi-degree of freedom nonlinear systems that experience narrow band random excitation, including an academic turbine blade model. In order to identify multiple and possibly ambiguous solutions, an efficient procedure is shown to integrate the mentioned method into a path continuation scheme. With this approach, it is possible to track jump phenomena or the influence of parameter variations even in case of narrow band excitation. The results of the performed calculations are the stochastic moments, i.e. mean value and variance.
Amplitude-Dependent Damping and Driving Rates of High-Frequency Thermoacoustic Oscillations in a Lab-Scale Lean-Premixed Gas Turbine Combustor
Authors: Hofmeister Thomas , Sattelmayer Thomas
Published: September 2021

This paper presents the numerical investigations of amplitude-dependent stability behavior of thermoacoustic oscillations at screech level frequencies in a lean-premixed, atmospheric, swirl-stabilized, lab-scale gas turbine combustor. A hybrid Computational Fluid Dynamics / Computational AeroAcoustics (CFD / CAA) approach is applied to individually compute thermoacoustic damping and driving rates for various acoustic amplitude levels at the combustors’ first transversal (T1) eigenfrequency. Harmonically forced CFD simulations with the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations mimic the real combustor’s rotating T1 eigenmode. A slow and monotonous increase of the forcing amplitude over time allows observation of the amplitude-dependent flow field and flame evolution. In accordance with measured OH*-chemiluminescence images, a pulsation amplitude-dependent flame contraction is reproduced in the CFD simulations, where acoustically induced backflow at the combustion chamber inlet is identified as the root-cause of this phenomenon. At several amplitude levels, period-averaged flow fields are then denoted as reference states, which serve as inputs for the CAA part. There, eigenfrequency simulations with linearized flow equations are performed with the Finite Element Method (FEM). The outcomes are damping and driving rates as a response to the amplitude dependency of the mean flow field, which combined give the net thermoacoustic growth rate. It is found that driving due to flame-acoustics interactions only governs a weak amplitude dependency, which agrees with prior, experimentally based studies at the authors’ institute. This disqualifies the perception of heat release saturation as the root-cause for limit-cycle oscillations — at least in this high-frequency thermoacoustic system. Instead, significantly increased dissipation due to the interaction of acoustically induced vorticity perturbations with the mean flow is identified, which may explain the formation of a limit-cycle.
Discrete Element Method Simulations of Additively Manufactured Components With Integrated Particle Dampers
Authors: Kiracofe Daniel , Postell Matthew , Scott-Emuakpor Onome , Runyon Brian , George Tommy
Published: September 2021

One major benefit of Additive Manufacturing is parts counts reduction. Several formerly distinct parts can be printed as one unit, reducing cost and weight. However, the interface between parts is often a major source of vibration damping, so eliminating interfaces can lead to fatigue failures. To alleviate this, researchers have been exploring the integration of damping features inside parts. Leaving a small pocket of unfused powder creates a particle damper. Particle dampers have long been known to suppress unwanted vibration. However they are highly complex and predicting their behavior is difficult. The particle damper literature often has contradictory claims, as what works best for one application does not work for another. Because the additive feedstock powder is much smaller (5–50 μm) than particles in typical particle dampers, it is difficult to draw conclusions from the existing literature to develop design guidelines. This papers reports on a Discrete Element Method (DEM) numerical simulation of additively manufactured cantilever beams with a small pocket of unfused powder. DEM explicitly simulates the motion of each particle and their interactions. Previously reported experiments with varying beam geometry showed nearly an order of magnitude difference in damping ratio depending on the location of the pocket along the beam. The simulation was able to accurately predict the damping ratio based on the input geometry. As a result, the correlated simulation tool can be used to optimize future designs. From the simulations, it was observed that particle-wall momentum exchange and particle-particle inelastic collisions appeared to be key contributors to the damping ratio. Additionally, a non-linear subharmonic motion of particles was observed, which suggests additional ways to improve performance.
The Influence of Condensation on the Performance Map of a Fuel Cell Turbocharger Turbine
Authors: Wittmann Tim , Lück Sebastian , Hertwig Tim , Bode Christoph , Friedrichs Jens
Published: September 2021

Exhaust gas of an automotive fuel cell is enriched with water vapour and has a pressure potential which can be utilized by a turbine. The gas expansion in the turbine leads to droplet nucleation and condensation. This results in a release of latent heat and a decrease of the gaseous mass flow which has a considerable influence on the turbine performance. This study aims to numerically investigate the influence of these phenomena on the performance map of the radial turbine of an automotive fuel cell turbocharger. For this purpose, the classical nucleation theory and Young’s droplet growth law are integrated into an Euler-Lagrange approach. The results show an almost linear relation between the pressure ratio and the condensation while the specific aerodynamics of an operating point has only a minor influence. At 80 % relative humidity of the inflow, the investigated turbine showed condensation above a total-to-static pressure ratio of 1.8. Condensation leads to thermal throttling of the turbine and to a temperature increase of the rotor outflow of up to 50 K. Increasing humidity of the inflow increases the power output, but condensation losses reduce the efficiency.
Micromechanical Modeling Tension-Compression Fatigue Hysteresis Loops Model of Fiber-Reinforced Ceramic-Matrix Composites Considering Fibers Failure
Authors: Li Longbiao
Published: September 2021

In this paper, a micromechanical tension-compression fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composite (CMC) was developed considering fibers failure. Multiple fatigue damage mechanisms of fibers failure, interface debonding, slip and wear, and matrix fragmentation were considered and incorporated in the micromechanical fatigue hysteresis loops model. Upon unloading, the unloading stress-strain relationship was divided into three stages, including, (1) Unloading Stage I: the unloading interface counter slip stage and the unloading stress is between the tensile peak stress and the matrix crack closure stress; (2) Unloading Stage II: the unloading partial compressive stage and the unloading stress is between the matrix crack closure stress and the unloading complete compressive stress; and (3) Unloading Stage III: the unloading complete compressive stage and the unloading stress is between the unloading complete compressive stress and the compressive valley stress. Multiple micromechanical damage parameters of fibers failure probability, unloading/reloading transition stress, closure stress of the matrix cracking, compressive transition stress, complete compressive stress, unloading/reloading inverse tangent modulus (ITM), and interface counter slip/new slip ratio (ICSR/INSR) were adopted to characterize the tension-compression stress-strain hysteresis loops. Experimental tension-compression fatigue stress-strain hysteresis loops of unidirectional CMCs were predicted using the developed micromechanical models. The characteristics of the tension-compression fatigue hysteresis loops of unidirectional CMC are analyzed for different material properties, damage state, and tensile fatigue peak stress.
A Novel Vibration-Based Fault Detection Approach of Bolted Engineering Structures Without Reference
Authors: Li Quankun , Shao Zengde , Liao Mingfu
Published: September 2021

Because of some advantages such as low cost, detachability and reusability, bolted joints are widely applied in various open beam-like engineering structures like steel beams and train rails and closed ring-type engineering structures like steel frames and oil pipelines to keep different structural components together. However, bolted engineering structures often encounter vibration-induced joint faults like self-loosening, crack, leakage and corrosion since they are generally subjected to external dynamic loads caused by vibration environments. Joint damages would seriously affect structures’ reliability and durability, and increase maintenance costs. Therefore, fault detection of bolted engineering structures is very important and necessary. For beam-like and ring-type engineering structures with single excitation and multiple damaged bolted joints, various methods monitoring changes in nonlinear structural features have been developed. To avoid the use of structural features from benchmark structures for reference during the derivation of damage indicators, a novel vibration-based fault detection approach utilizing features from damaged structures only is proposed in this study. In the new method, the dynamic model of bolted engineering structures is simplified as a general MDOF model with nonlinear elements simulating nonlinear bolt loosening faults. By changing the value of related mass, three similar equations from the damaged structure are used to form one matrix, and then the singularity of matrix is used to detect the existence and position of faults. Results from simulations on the beam-like and ring-type models with multiple damages demonstrate that the proposed approach could be an effective tool to estimate the state of bolted engineering structures.
A Novel Test Rig Using Air for Investigation of Vibration and Interaction of Two Steam Turbine Control Valves
Authors: Wallat Stefan , Preibisch Stefan , Strauch Matthias , Brillert Dieter
Published: September 2021

The governing of steam turbines is often realised by a set of two or more valves, which control the amount of steam entering the turbine. During part-load operation forces caused by pressure fluctuations, turbulence etc. are acting on the throttling valve and lead to spindle vibrations. Besides these mechanisms, it is assumed that there is also an interaction between the control valves, which leads to another source of vibration.

In this paper, the design of a new test rig using air with two parallel control valves is presented. One aspect of the design is the chosen scaling method, which includes material selection for the valve spindle, and ensures comparability and transferability of the vibrational behaviour to the full scale with steam. Another aspect is the selection of measurement equipment.

The results show that the reasons for valve vibrations can be located both upstream and downstream of the valve seat. Forces caused by pressure fluctuations in and behind the valve gap lead to similar oscillations at both valves. In addition, the upstream valve causes disturbances that lead to partly differing behaviour of the second valve.
Simulation of Passing Wakes Inducing Unsteady Boundary Layer Transition Around Low-Pressure Turbine Blade
Authors: Dufau Antoine , Marty Julien , Man Daniel , Piot Estelle
Published: September 2021

The present study focuses on the very high-lift T106C cascade with passing wakes and aims to validate the γ - Re θ ¯ model of Menter-Langtry used to predict laminar-turbulent transition based on unsteady Reynolds-Averaged Navier-Stokes simulations. The comparison to experimental data provided by Von Karman Institute, shows that the transition model is able to capture the influence of passing wakes on transition phenomenon. Like the experiments, the simulations show a reduction of the time-averaged separation bubble length and of the overall losses in the presence of passing wakes. For this numerical study, four other wakes have been generated in order to study the influence of wake parameters on the transition onset, on the laminar separation bubble formation and on the turbine cascade performances. For a given averaged turbulence intensity and total pressure deficit, thinner wakes seem to have a more positive effect on boundary layer, reducing the separation and the overall losses.
Improved Rotor Design With Combined 3D-2D Probabilistic Approach
Authors: Schuchard Lukas , Voigt Matthias , Mailach Ronald , Dumstorff Peter , de Lazzer Armin , Almstedt Henning
Published: September 2021

Availability and flexibility, largely in terms of start-up times, are becoming paramount for today’s steam turbine operation. Thus, precise knowledge of the stresses components experience and their lifetime consumption in transient regimes is vital for safe turbine operation. A typical lifetime-driving feature is low cycle fatigue in rotor grooves that is caused by rotor-blade root interaction and thermo-mechanical stresses.

In the course of a previous project at Technische Universität Dresden [1, 2] a 2D axisymmetric, transient thermo-mechanical model of an intermediate pressure steam turbine rotor had been developed for probabilistic analysis. Thereby, the blade root compound’s stiffness and the twisting of rhomboid blade roots in circumferential grooves, both of which cannot be modelled directly in 2D, were found to be key drivers for uncertainties in lifetime calculation.

To overcome these limitations, a 3D four-stage, fifteen-blade mechanical model for further analysis was created. The present work introduces this 3D model. It is then employed in a probabilistic sensitivity study to further refine the understanding of the influence of unknown or uncertain boundary conditions on the stresses that drive lifetime consumption. These results for stationary and exemplary transient operation are fed back into fine-tuning the existing 2D model in order to match the 3D calculated stresses. With its far lower computational effort the improved 2D model is well-suited for efficient future probabilistic analysis for robustness estimation and design space exploration.
Synergistic Effect of Soot Formation in Ethylene/Propane Co-Flow Diffusion Flames at Elevated Pressures
Authors: Zheng Dongsheng , Hui Xin , Xue Xin , Liu Weitao
Published: September 2021

The synergistic effect of soot formation refers to the interaction between different fuels during soot forming processes, which results in higher soot formation than any individual fuels. The present study experimentally investigates the synergistic effect of soot formation in co-flow diffusion flames of propane/ethylene fuel mixtures. The total carbon mass flow rate of the propane/ethylene mixture was kept constant at 0.5 mg/s, and the propane carbon ratio (RC) was defined as the ratio of carbon mass flow rate of propane to the total carbon mass flow rate. The laser-induced incandescence (LII) and light extinction (LE) techniques were applied to measure the soot volume fractions (SVF) at pressures of 0.1–0.5 MPa. The results showed strong synergistic effect in propane/ethylene mixtures at atmospheric conditions; however, increasing pressure weakens the synergistic effect. The LII intensity contours showed that the soot formation zone extends when synergistic effect occurs at RC = 0.1 and 0.2 for 0.1 and 0.3 Mpa. The normalized peak SVF showed that synergistic effect monotonically becomes weak with increasing pressure from 0.1 to 0.3 Mpa; meanwhile, the it still stayed strong at 0.2 Mpa when using normalized maximum soot yield, and then turned to be weaker as pressure increases. Further comparison analysis of the SVF profiles between RC = 0 and 0.1 revealed that the synergistic effect occurs at the two-wing area of the sooty flame at low axial flame height, and then gradually becomes stronger with increasing axial flame height in the soot zone for 0.1–0.3 Mpa. To illustrate the pressure effects on synergistic soot formation, numerical analysis in homogeneous closed reactor was conducted and it was found that The PAHs formation competition between C3H3 pathway and HACA mechanism results in the different soot formation phenomenon of ethylene/propane flames.
The Development Problems of Two-Fuel Burner for the Gas Turbine Combustion Chamber
Authors: Vasilyev A. Yu , Chelebyan O. G. , Maiorova A. I. , Tarasenko A. N. , Tarasov D. S. , Zakharov V. M.
Published: September 2021

The work is devoted to the design of a spraying device for the combustion chamber GTE-65.1 on liquid fuel.

The paper presents the following results:

1) The 3D calculations of the air channels characteristics for two burners types — pilot and main — were carried out. Data were obtained on the flow and pressure fields inside and at the burners outlet, and also the volumes of the reverse flow zones.

2) The main and pilot nozzles have been designed for the two spraying devices types. The values of droplet dispersity and spray angle were obtained, depending on the fuel injection pressure.

3) Based on the calculations carried out, the models of two spraying liquid fuel devices were designed and manufactured, the design of which is based on the design of the single-fuel combustion chamber (CC) on natural gas burners for GTE-65.1.

At the next stage of the work, it is planned to carry out experimental studies of the two devices models aimed at obtaining an aerosol mixture with the desired properties to ensure uninterrupted operation of the GTE-65.1 on liquid fuel. Some preliminary experimental data are presented in this paper.
Inlet Distortion Simulations of a Transonic Fan With CFD and Low-Order Methods
Authors: Favaron Carlo , Magrini Andrea , Visentin Alessandro , Menegozzo Luca , Benini Ernesto
Published: September 2021

Future aircraft are expected to have a high level of fuselage-engine integration, exposing the propulsor to non-uniform inflow conditions, in which the performance and stability of the engine fan can be severly affected. This paper proposes a study of a transonic fan subject to inlet distortion by employing steady RANS simulations and mean line calculations. The steady CFD results, although insufficient to correctly measure the interaction of the distortion across the cascade passages, are used as a benchmark to compare the prediction of a leaner low-order tool, adopting a superposition of several 1D calculations in the discretised compressor approach. A continuous total pressure deficit is imposed at the inlet and the distorted operating points are compared to the clean inflow case. The performance drop at the peak efficiency point is similar for the two models, altough the mean-line 1D method fails in closely matching the distribution in the upper span of the blade. The qualitatively similar response of the low-order approach to the distorted inflow should allow for its use in preliminary blade design exploration once improved for high-speed flow prediction.