bluuebunny/crossref_metadata_2025 huggingface dataset:
Retinal Occlusive Vasculitis after Intravitreal Injection of Brolucizumab
Authors: Lee Jong Hoon , Moon Tae Kyu , Ji Yong-Sok
Published: February 2024

Purpose: To report two instances of retinal arterial occlusive vasculitis following intravitreal injection of brolucizumab.Case summary: Two patients noted decreased visual acuity approximately one month after receiving intravitreal brolucizumab injections to treat wet age-related macular degeneration. In case 1, an 85-year-old male reported a reduction in visual acuity in his left eye, declining from a Snellen measurement of 0.2 to hand motion. In case 2, a 70-year-old female experienced a decline in visual acuity in her right eye from 0.4 to finger count at 50 cm. Both patients presented with anterior chamber reactions, and fluorescein angiography demonstrated delayed retinal artery filling time, leading to the diagnosis of retinal occlusive vasculitis. They were treated with both topical and systemic corticosteroids. For case 1, a subsequent vitrectomy was performed to remove the inflammatory membrane located behind the intraocular lens. However, despite aggressive interventions, neither patient showed visual improvement.Conclusions: Retinal occlusive vasculitis, which can result from intraocular inflammation, may occur after intravitreal brolucizumab injection. This condition can lead to significant visual impairment even with aggressive treatment.
An Adolescent Case of Unilateral Papillophlebitis Treated with Intravitreal Bevacizumab
Authors: Seo Bo Kang , Lee Jaehyuk , Park Jihae
Published: February 2024

Purpose: To report a case of papillophlebitis treated with an intravitreal bevacizumab injection in an adolescent patient.Case summary: A 15-year-old female with no medical history presented with a 3-day history of blurred vision and a floating sensation. The initial visual acuity (VA) was 0.0 logarithm of minimal angle of resolution (logMAR) in the left eye. A fundus examination revealed a blurry disc margin, peripapillary hemorrhage, and venous engorgement. Optical coherence tomography indicated subretinal fluid (SRF) accumulation. Both color vision and pupillary reactions were normal in bilateral eyes. Blood tests revealed no significant abnormalities. Brain magnetic resonance imaging (MRI) showed mild focal papillitis, but the patient did not report eye movement pain or discomfort. The diagnosis was papillophlebitis; however, high-dose steroid treatment was not initiated due to the absence of a significant decrease in VA. A single injection of intravitreal bevacizumab was administered to address the SRF. At the 9-month follow-up, VA remained at 0.0 logMAR, and the retina demonstrated anatomical stabilization after complete absorption of the SRF without recurrence.Conclusions: Papillophlebitis can manifest during adolescence. Treatment of a 15-year-old patient with intravitreal bevacizumab obviated the need for high-dose steroid therapy and produced favorable outcomes, including preservation of VA and anatomical stabilization of the retina.
Interactions of Corneal Endothelial Cells with Stromal Cells during Corneal Endothelial Injury
Authors: Kim Kyung Wook , Shin Young Joo
Published: February 2024

Purpose: To investigate the interaction of corneal endothelial cells (CECs) with corneal stromal cells (CSCs) on the healing of chemically induced corneal endothelial injury.Methods: Twenty-five rabbits were divided into two groups: rabbits exposed to NaOH and controls. Rabbits were clinically evaluated and sacrificed at 1 day, 1 week, 2 weeks, and 4 weeks after endothelial injury. Corneal endothelial cells and corneal stromal cells were cultured and the wound healing rate of the corneal endothelium and cytokines in the culture medium were analyzed with and without co-culture in the Transwell system.Results: Corneal edema and opacity scores were higher in all rabbits exposed to NaOH than in controls. Corneal endothelial apoptosis with little effect on CSCs was observed in rabbits exposed to NaOH at day 1. Two weeks after injury, CECs migrated from the periphery. CSCs were aligned in parallel to Descemet's membrane, which exhibited the presence of CECs. Transforming factor-β1 and interleukin-6 secretion was lower in the co-culture system than in individual cultures of CECs or CSCs.Conclusions: These results revealed intracameral NaOH injection is a model of corneal endothelial injury with minimal impact on the stroma. Communication between CECs and CSCs during wound healing may lead to the modulation of cytokine production, which is necessary for an enhanced healing process of corneal endothelial injury.
Advancing Women's Rights to Joint Ownership of Matrimonial Property in Nigeria: Using Kenya as a Model
Authors: Ehiemua Roseline Omoye
Published: February 2024

This article critically reviews the concept of matrimonial property in Nigeria, with particular reference to real property and the rights of spouses to it during marriage dissolution, against the backdrop of extant statutes and case law on the subject, and makes a case for a reform using Kenya’s progress in this area of law as a model. It identifies gaps and inconsistencies in the existing statutes and case law on the subject in Nigeria which render many verdicts controversial, unsatisfactory and inequitable. First, the reviewed literature identifies that neither statute nor case law proffers a definition of matrimonial property. Secondly, the only criterion in the Matrimonial Causes Act 1970 for sharing property amongst spouses upon divorce, which is to the Judges’ discretion, has often been wrongly applied to stress substantial contribution in financial terms. This is due to the fact that the common law principle adopted in matrimonial property sharing upon dissolution of all types of marriages in Nigeria stresses substantial contribution in financial terms. This common criterion is unrealistic in light of modern global and local economic, social, and cultural realities; its application is also obsolete in the English jurisdiction where it originated. This paper therefore makes a case for the emergence of a law which will define matrimonial property and also specifically state the rights of spouses and resolve lingering issues of inconsistencies and lack of fairness arising from both the existing statutes and case law using Kenya’s progress in matrimonial property system as a model.
Assessment of a body force modeling approach to examine the aerodynamics of high bypass ratio fan stages
Authors:   TU Braunschweig - Institute of jet propulsion and turbomachinery, Grubert Jonas , Göing Jan ,   TU Braunschweig - Institute of jet propulsion and turbomachinery, Friedrichs Jens ,   TU Braunschweig - Institute of jet propulsion and turbomachinery
Published: February 2024

The primary focus of modern civil jet engine intake design is to enhance propulsive efficiency through an increase in the bypass ratio of the turbofan engine, which requires an enlargement in fan diameter. However, this enlargement results in increased weight and drag due to the need for a larger nacelle to surround the fan. To mitigate these issues, efforts are being made to shorten the axial length of the aircraft engine intakes. Nonetheless, this reduction leads to more vulnerable fan aerodynamics since the diffusion within the intake must occur over a shorter distance, causing a higher possibility of flow separation. Common intake design methods employ throughflow nacelle models that do not consider the aerodynamic effects of the fan, including blockage, mass flow redistribution, and suction. The utilization of a full annulus domain numerical setup, which is necessary to capture inlet distortions, demands excessive computational resources particularly during the design phase. As a result, reduced order models, such as the body force model, can be utilized to simulate fan intake aerodynamics. This paper will assess the body force model and its abilities by comparing conventional bladed single passage simulations with the body force approach.
The Impact of Variable Fillets on Corner Separation in a Liner Compressor Cascade
Authors:   School of Aeronautics and Astronautics Shanghai Jiao Tong University, Zhang Gangduo , Shao Runzhu ,   School of Aeronautics and Astronautics Shanghai Jiao Tong University, Zhu* Mingmin ,   School of Aeronautics and Astronautics Shanghai Jiao Tong University, Qiang Xiaoqing ,   School of Aeronautics and Astronautics Shanghai Jiao Tong University, Teng Jinfang ,   School of Aeronautics and Astronautics Shanghai Jiao Tong University
Published: February 2024

The performance of highly-loaded compressor is restricted by complex three-dimensional corner separation. The fillet with variable geometry around the blade has shown its potential in reducing the corner separation. However, there are no specific design criteria for fillets. Additionally, the impact of variable fillets on flow mechanisms and unsteady flow phenomena remains unclear. In this paper, the NACA65-K48 cascade profile without a fillet is used as a baseline. A parametric design method is developed to generate fillets with uniform and variable profiles along the axial direction. Cascades with two uniform and three variable fillets are profiled to explore the effect and flow mechanisms of fillet sizes. Steady numerical simulations are carried out in these cascades at different attack angle conditions. Compared with uniform fillets, all three variable fillets are able to improve performance at near-stall point without degradation at other attack angles. The fillet with size increasing and gradually decreasing along the chord has the best performance improvement within the full attack angle range. Analysis of axial and spanwise wall shears indicates that uniform fillets lift the separation area upward as a whole, while variable fillets eliminate small endwall separation and significantly reduce large-scale corner separation to decrease losses over the entire operating range. To further elaborate the key flow and loss mechanisms, unsteady simulations are conducted with the Stress Blended Eddy Simulation (SBES) model. SBES simulations predict near stall conditions comparable to steady results. The results demonstrate that variable fillets reduce corner separation by smoothing transition between blade and endwall and reducing transverse pressure gradient. The configuration with increasing then decreasing fillet size shows the greatest potential for improving performance, by suppressing additional trailing edge separation caused by large fillet size.
An automatic mesh generation system for aeroengine blade design and optimization
Authors:   Department of Mechanical Engineering City University of Hong Kong, Fan Jiazheng , Han Chuang ,   Suzhou NuFlux Technology Co., Ltd, Wu Yongxiang ,   University of Stuttgart, Li Weihong ,   Department of Mechanical Engineering City University of Hong Kong, Duan* Penghao ,   Department of Mechanical Engineering City University of Hong Kong
Published: February 2024

Mesh generation in blade design is time-consuming and involves plenty of manual operations. The mesh quality directly influences the accuracy of the CFD simulation (Baker, 2005). In this study, a mesh generator is developed to automatically produce high-quality mesh for the CFD simulation of the aero-engine blade. The system first uses a parameterization system to generate the blade profiles and the blocking lines in the computational domain. Then, the transfinite interpolation method is adopted to automatically produce the mesh from the blocking lines. Several mesh control parameters can be assigned to change the distribution law and the density of the mesh nodes to guarantee the quality of the mesh. A mesh quality check system examines the mesh using several characteristic parameters, such as Jacobian ratio, warping factor, skewness, etc. The statistical distributions of these parameters in the computational domain are validated against the commercial software, ICEM CFD, using the same mesh. The low-quality cells can be highlighted in red as references for the mesh quality improvement. Based on these technologies, a turbine blade CFD calculation platform is built using the open-source software OpenFOAM. The integrated system can accelerate the aero-engine blade design cycle and be used in blade design optimization.
Unsteady flow phenomenon in the TUDA-GLR-Openstage compressor: URANS observations
Authors:   School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Deng Hefang , He Xiao ,   Department of Aeronautics, Imperial College London, Zhu Mingmin ,   School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Klausmann Fabian ,   Institute of Gas Turbines and Aerospace Propulsion, Technische Universit ¨ at Darmstadt, Teng Jinfang ,   School of Aeronautics and Astronautics, Shanghai Jiao Tong University
Published: February 2024

Unsteady flow phenomenon plays a critical role in determining the aerodynamic performance and stability of a compressor. In this study, the unsteady flow phenomena in the TUDa-GLR-OpenStage compressor at stable operating conditions were investigated through unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations. The URANS results were first validated against measured data in terms of mean flow quantities and unsteady fluctuations. Then, the unsteady flow phenomena and their associated flow mechanisms in the rotor tip region, the stator hub region, and the stator hub cavity were discussed in detail. The results show that at the rotor tip, URANS captures the fluctuations associated with the blade passing frequency (BPF) and its harmonics, but it fails to capture sub-BPF fluctuations of tip leakage flow observed in the measured data. At the stator hub, URANS captures the rotor-stator interaction at the BPF, and the unsteady fluctuation of stator hub corner separation with the rotor wake phase is analyzed. At the stator hub cavity, URANS captures a broadband low-frequency signal in the cavity exit channel, which corresponds to the pumping mode of the blockage cells that leads to the unsteady fluctuation of leakage flow rate. These results provide valuable information on the unsteady flow mechanisms of the investigated compressor and the capability of URANS simulations for predicting compressor flows at stable operating conditions.
The effects of Reynolds number on the instability boundary and dynamic characteristic of an axial-centrifugal combined compressor
Authors:   Institute for Aero Engine, Tsinghua University, Kong Weihan , Wang Baotong ,   Institute for Aero Engine, Tsinghua University, Li Jiaan ,   School of Vehicle and Mobility, Tsinghua University, Zheng Xinqian ,   School of Vehicle and Mobility, Tsinghua University
Published: February 2024

The axial-centrifugal combined compressor is the core component of an aero turboshaft engine. The low-Reynoldsnumber effect caused by the increased flight altitude deteriorates the compressor's stability and restricts the aero-engine's stable working range. This paper numerically investigates the influence mechanism of the Reynolds number on the aerodynamic stability of an axial-centrifugal combined compressor. By establishing a 1D/3D coupling model with the γ- Reθ turbulent transition model in the 3D flow modelling, the simulation reaches a 2% accuracy of instability boundary prediction, compared with the experimental results. The results show that in the condition of high-Reynolds-number, the instability initiates from the centrifugal stage of the compressor. However, with the decrease of Reynolds number, the component where the instability initiates moves from the last centrifugal stage to the upstream axial stages, which makes the stable working margin drop significantly. Furthermore, the low-Reynolds-number lowers the pressurization capability in the compressor system, which increases the time of the re-pressurization stage in a surge cycle.
Development of an axial flow fan with alternating blade lengths
Authors:   Stellenbosch University, Le Roux Tristan O. , van der Spuy Sybrand J. ,   Stellenbosch University, von Backström Theodor W. ,   Stellenbosch University
Published: February 2024

To reduce the effect of backflow at the hub of an axial flow fan, it was proposed to use an alternating blade length design instead of a constant blade length design. This allows a redistribution of the flow through the fan, which induces higher through-flow velocities at the hub and consequently reduces the tendency for backflow to occur by 42.56%. However, the increased tip clearance induces higher pressure losses, reducing the fan’s efficiency by a maximum of 2% (absolute) at the designed operating pressure rise, while causing the fan to operate closer to the stall point.
Effects of increased tip clearance on the unsteady flow behaviors at near-stall condition in a counter-rotating axial flow compressor based on POD method
Authors:   School of Power and Energy,Northwestern Polytechnical University, Zhang Ruichen , Mao* Xiaochen ,   School of Power and Energy,Northwestern Polytechnical University, Liu Bo ,   School of Power and Energy,Northwestern Polytechnical University, Wang Lei ,   School of Power and Energy,Northwestern Polytechnical University, Zhang Botao ,   School of Power and Energy,Northwestern Polytechnical University
Published: February 2024

To explore the effects of increased tip clearance on the unsteady flow behaviors at near-stall point (NSP) of a counter rotating axial flow compressor (CRAC) and its related physical mechanisms, this paper perform a deep comparative analysis of unsteady numerical simulation results of a two-stage CRAC at different tip clearance size (TCS), in combination with the Proper Orthogonal Decomposition (POD) method. From the results, it can be seen that the rear rotor (R2) leading edge (LE) has greater unsteady fluctuation intensity than the front rotor (R1) passage at different TCS. Potential flow interference from R2 causes higher static pressure fluctuations at R1 pressure surface (PS) and outlet than tip leakage flow (TLF). The unsteady fluctuation at the LE of R2 is more severe at large TCS. Frequency analysis indicates an increased frequency of TLF for R2. The POD analysis confirms the above conclusions and reveals the dominant structures and their influence range in the unsteady flow field at different TCS. Increased TCS leads to larger scale spillage structure at LE of R2, more complex mode composition, and higher energy contribution in the flow field.
Numerical modeling of tubular reactor for catalytic hydrogen generation via ammonia decomposition
Authors:   Department of Applied Physics, The Hong Kong Polytechnic University, Lin Yashan , Zhang Zijian ,   Department of Aeronautical and Aviation Engineering, The Hong Kong Polytechnic University, Li Zhengtong ,   Department of Aeronautical and Aviation Engineering, The Hong Kong Polytechnic University, Wen Chih-Yung ,   Department of Aeronautical and Aviation Engineering, The Hong Kong Polytechnic University, Li Molly Meng-Jung ,   Department of Applied Physics, The Hong Kong Polytechnic University
Published: February 2024

Hydrogen (H2) has been considered as a potential energy storage solution. However, the costly and technology-intensive infrastructure required for H2 transportation and storage has hindered its widespread adoption. Ammonia (NH3)- based energy storage system is thus emerging as a promising alternative for storing and producing H2 without carbon emissions. However, the investigation of practical scale NH3-to-H2 reactor systems is strongly impeded by their labour-intensive and time-consuming features. Employing the computational fluid dynamic (CFD) simulation, we establish a two-dimensional model of a typical tubular fixed-bed reactor for NH3 decomposition on our recently developed Ru/NiO composite catalyst. NH3 conversion and H2 production for fuel cell applications are theoretically and numerically predicted. Through a series of numerical simulations and experimental verifications, the underlying impact of catalyst porosity and inlet gas temperature on system performance is further investigated. The result shows that, at 500 °C, the NH3 conversion can enhance from 13% to 49% with increasing porosity from 0.2 to 0.8, and from 47% to 86% by preheating inlet gas to wall temperatures. This work provides potential solutions for developing a scalable process to produce H2, giving rise to a future reference and inspiration for clean energy development and applications.
Research on matching failure mechanism of low-pressure turbine under low working condition
Authors:   College of Power and Energy Engineering, Harbin Engineering University, Zhang Han , Zuo Xuan ,   College of Power and Energy Engineering, Harbin Engineering University, Wu Lei ,   College of Power and Energy Engineering, Harbin Engineering University, Gao* Jie ,   College of Power and Energy Engineering, Harbin Engineering University, Huo Dongchen ,   College of Power and Energy Engineering, Harbin Engineering University
Published: February 2024

In order to clarify the failure mechanism of low-pressure turbine matching under low working conditions, the numerical simulation of a low-pressure turbine under design condition and low working conditions are carried out. The results show that under low working conditions, the isentropic expansion efficiency of the low-pressure turbine decreases by more than 1.69%. Large total pressure losses exist on both vane and rotor in low pressure turbine. The upper passage vortex core moves down and the lower passage vortex core moves up, and low energy fluid in the endwall boundary layer flows to the midspan. Under the influence of low energy fluid from the vane trailing edge, the size and intensity of the tip leakage vortex in 95% vane span becomes larger, and the large passage vortex appears at the midspan of the rotor. The reduced turbine efficiency is mainly caused by low energy fluid from vane trailing edge, tip leakage vortex of the rotor and passage vortex of the midspan of the rotor.
Deriving Sensitivities of Distributed Propeller Propulsion in Overwing Configuration by using DoE in CFD Simulations
Authors:   Technische Universität Braunschweig, Kirsch Bastian , Friedrichs Jens ,   Technische Universität Braunschweig
Published: February 2024

In this publication the interaction of propeller and wing of a short haul aircraft concept with distributed propeller propulsion in an over-wing configuration at cruise conditions is investigated. The numerical studies are performed in the CFD solver TAU of the German Aerospace Center using the Actuator Disk together with a wing segment with constant chord length. All calculations are performed in trimmed condition, i.e. with constant lift and drag coefficients. The resulting propeller power is used as a comparative variable. In order to quantify the influences of the position in chord direction, distance to the wing surface, installation angle, propeller diameter as well as distance between the propellers, a design of experiments approach with face centered central composite design is used. The resulting regression model is shown and analyzed. The procedure is carried out with two different propeller designs. In the first run, a propeller designed for a conventional aircraft with one propeller per half span is used. In the second run, a propeller designed for a distributed propulsion concept facing lower loads is used. The changes in the regression models are shown and compared. It hast been shown that the chord position has a significant influence on the performance of the propeller. The lowest power is reached when the propeller is positioned above the trailing edge of the wing. In addition, there is a dependence on the installation angle, which roughly follows the surface curvature of the airfoil. For the distance to the top of the wing, only a negligible effect on the propeller performance was found. For a positioning above the trailing edge, the propeller diameter and the spanwise distance between the propellers were found to be dominant parameters. Even when using a different propeller design, the linear dependence remains. For both propellers investigated, there is a similar optimal combination of diameter and spanwise distance with lowest power.
Particulate Deposition Effects in Film Cooling Holes
Authors:   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery,School of Energy & Power Engineering, Xi’an Jiaotong University, Hao Zihan , Yang* Xing ,   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery,School of Energy & Power Engineering, Xi’an Jiaotong University, Feng* Zhenping ,   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery,School of Energy & Power Engineering, Xi’an Jiaotong University
Published: February 2024

The dust, sand, and other micron-sized particles in the atmosphere are usually drawn into the gas turbine and diverted into the secondary cooling air, which further travel to the internal cooling channel and are prone to deposit on the internal surfaces of the hot section due to elevated temperatures. These deposits block the cooling channels and film cooling holes, leading to the deterioration of cooling performance of turbine blades. The present study investigates the migration patterns and deposition distributions in film cooling holes in terms of different coolant supply methods, i.e. co-flow, counter-flow, plenum-flow, and cross-flow, which are typically seen in a real turbine cooling design. The growth of the deposits is modelled through a mesh morphing method and the resulting changes of cooling performance are analysed by simulating an event of 2,200 hours exposure. Results show that the co-flow coolant supply causes particle deposition close to the exit of the film cooling holes, while the deposits are mainly concentrated on the rear half section with the other coolant supply methods. The cooling performance substantially degrades under the cross-flow scheme, while an increase is observed in the plenum-flow provision after the deposition of the particles.
Evaluation of the cooling flow rate of the cooled steam turbine for a novel h2/o2 cycle
Authors:   Shanghai Jiao Tong University, Ma Bangyan , Li Yan ,   China United Gas Turbine Technology Co.Ltd, Shi Lei ,   Shanghai Jiao Tong University, Zhu Xiaocheng ,   Shanghai Jiao Tong University, Du Zhaohui ,   Shanghai Jiao Tong University
Published: February 2024

In recent years, with the global low-carbon development, hydrogen as a clean fuel for the industry has attracted the interest of many research institutions all over the world. The potential of hydrogen energy in energy transformation has been paid attention to again. Power generation systems based on hydrogen could be an important alternative to conventional power systems based on the combustion of fossil fuels. Mixed hydrogen and pure hydrogen combustion in gas turbines is an important technological path to achieve carbon neutrality. It is sure that the cycle efficiency is influenced by the turbine efficiency and cooling flow rate. Therefore, when assessing the performance of novel cycles, it is necessary to perform a preliminary evaluation of the turbine efficiency and cooling flow requirements based on a few (or even without) experimental data. In this paper, a methodology is proposed for the preliminary evaluation of the turbine efficiency and cooling flow requirements of a novel cycle based on the Hydrogen-Fueled Combustion Turbine Cycle. When both the working fluid and coolant are steam, the cooling flow rate is less. Preliminary results for the novel H2/O2 cycle turbine show that part of the stages need to be cooled and the film cooling effectiveness is less.
Numerical stability analysis of solution methods for steady and harmonic balance equations
Authors:   Northwestern Polytechnical University, Zhang Yuxuan , Wang Dingxi ,   Northwestern Polytechnical University
Published: February 2024

This study presents an investigation into the stability and convergence properties of solution methods for the steady and unsteady Euler equations. A central scheme with artificial dissipation is used for the spatial discretization, and a Runge- Kutta scheme with or without implicit residual smoothing, such as LU-SGS for a steady solution and LU-SGS/BJ for an unsteady solution, is used for time integration. Both the von Neumann and matrix methods are used to analyze the stability of the involved solution methods. The stability of these schemes obtained by the two stability analysis methods is identical for periodic boundary conditions as expected. However, with inlet, outlet and slip wall boundary conditions, the stability can be analyzed using the matrix method only. It is found that these boundary conditions enhance stability of solution methods. Additionally, the matrix method can also allow for the analysis of the impacts of non-uniformity in grids and flow fields, as well as second-order artificial dissipation. For the unsteady Euler equations solved using the harmonic balance method, the stability analysis demonstrates that the time spectral source term must be handled implicitly to avoid instability for analysis with high grid-reduced frequency. The conclusions can be readily extended to the RANS equations and verified in a nozzle and the NASA rotor 37.
Conjugate Heat Transfer Characteristics of Narrow Channels in Double-Wall Cooling System with Variable-Size Pin Fins and Film Holes
Authors:   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery, School of Energy & Power Engineering, Xi’an Jiaotong University, Wang Yi , Hu Qingsong ,   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery, School of Energy & Power Engineering, Xi’an Jiaotong University, Wang Xiangyu ,   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery, School of Energy & Power Engineering, Xi’an Jiaotong University, Feng* Zhenping ,   Shaanxi Engineering Laboratory of Turbomachinery and Power Equipment, Institute of Turbomachinery, School of Energy & Power Engineering, Xi’an Jiaotong University
Published: February 2024

In an Impingement-Pin-Fin (IPF) cooling system, the arrangement and the size of the pin fin may change flow fields and the conjugate heat transfer characteristics. Different target plates are investigated, including six flat plates and six effusion plates with different pin fin diameters (uniform diameter, linear diameter increase, and linear diameter decrease) along the flow direction. And the conjugate heat transfer method has been used to predict the conjugate heat transfer characteristics. This study attempts to change the diameter of the pin fin to affect the flow area of the coolant along the streamwise direction, and then adjust the development of the generated crossflow in the narrow channel. The results show that the change of the pin fin diameter along the streamwise direction has a great influence on the heat transfer level and the crossflow in the IPF cooling system. The Decrease design has a good effect on crossflow suppression, and the Increase design is the opposite. The presence of film holes will effectively suppress crossflow and weaken the influence of pin fins.
Impact force of ellipsoidal droplets on superhydrophobic surfaces
Authors:   Department of Mechanical Engineering, The Hong Kong Polytechnic University, Ray Saroj , Cheng* Song ,   Department of Mechanical Engineering, The Hong Kong Polytechnic University
Published: February 2024

Although wind turbine technology has emerged as an important renewable energy source, the unpredictable operating environment poses significant challenges in normal operation. Rain and hailstorm cause erosion on the leading edge of the Wind Turbine Blades (WTBs). As WTB get eroded, its performance diminishes and frequent repairs raise maintenance costs. The impact dynamics of non-spherical water droplets on a solid surface are investigated numerically in the present study. The finite volume method is utilized to solve the Navier-stokes equation and continuity equation, while the interface is accurately tracked through the implementation of the geometric Volume of Fluid (VOF) method. The effect of droplet morphology on the impact force is analyzed. Results show that the peak impact force increases with increasing aspect ratio at fixed Weber number. A correlation for dimensionless peak impact force based on aspect ratio is proposed. The maximum impact force obtained in this study can aid in the decision-making during the design and material selection of WTBs.
Application of surrogate models based on cfd database for performance prediction of transonic compressors
Authors:   School of Power and Energy, Northwestern Polytechnical University, Han Zichen , Chen Zijing ,   School of Power and Energy, Northwestern Polytechnical University, Mao Xiaochen ,   School of Power and Energy, Northwestern Polytechnical University, Liu Bo ,   School of Power and Energy, Northwestern Polytechnical University
Published: February 2024

While evaluating the performance of a high-load transonic axial-flow compressor with strong 3-D effects, the applicability of empirical correlations between loss and deviation angle is limited. For this reason, the surrogate models of loss and deviation angle using the feedforward neural network algorithm was built in the paper. Based on the CFD calculation results of four single-stage transonic compressors at multiple rotational speeds, a database of super-transonic flow considering 3-D effects was constructed for training surrogate models, with the rotor and stator data partitioned. In order to test the performance of the surrogate models, the models were integrated into a throughflow program based on the streamline curvature method (SLC) to predict the compressor characteristics, and the predicted characteristic results with the empirical models and surrogate models were compared for the compressors. The results showed that, the surrogate models improved the prediction accuracy of the pressure ratio and efficiency, and more accurately captured the trend of the spanwise distribution of loss and deviation angle. After the database was expanded to 4 compressors, it was found that the universality of rotor models would decrease. At high rotational speed conditions, the model's prediction results were interfered by the data from other compressors. Meanwhile, the surrogate models had good universality in the prediction of stator.
Numerical study of the reynolds number on the energy losses inside centrifugal compressor
Authors:   Key Laboratory of Light-duty Gasturbine/ Institute of Engineering Thermophysics, Chinese Academy of Sciences, LI ZiLiang , HAN Ge ,   Key Laboratory of Light-duty Gasturbine/ Institute of Engineering Thermophysics, Chinese Academy of Sciences, LU XinGen ,   Key Laboratory of Light-duty Gasturbine/ Institute of Engineering Thermophysics, Chinese Academy of Sciences, LI Lin ,   Key Laboratory of Light-duty Gasturbine/ Institute of Engineering Thermophysics, Chinese Academy of Sciences
Published: February 2024

The increasing demand for more efficient energy conversion is making it extremely difficult for designers to develop next generation of centrifugal compressors. As the Reynolds number in centrifugal compressor operation decreases with increasing flight altitude, the efficiency degradation associated with it has been a key limitation to the energy conversion efficiency of aircraft engines. In this paper, the performance and internal flow field of a centrifugal compressor for a rear stage of a combined compressor are numerically simulated under different inlet conditions. The sources of efficiency degradation under low Reynolds numbers are discussed. Under low Reynolds numbers, the thermodynamic process in the compressor deviates more and more from the isentropic process. By establishing a way to classify different types of energy losses, the variation of different types of losses inside the impeller and diffuser are compared under different Renolds number. The results show that, when the boundary layer loss in the impeller increases as Reynolds number decreases, the recirculation loss and secondary flow loss also increase, which leads to a more obvious performance degradation. On the contrary, in the diffuser, the energy loss originally dominated by the boundary layer loss and the main flow loss, after the Reynolds number decreases, the boundary layer loss becomes the only source.
An Efficient Multi-Fidelity Simulation Approach for Performance Prediction of Adaptive Cycle Engines
Authors:   Tsinghua University, Zou Wangzhi , Wang Baotong ,   Tsinghua University, Song Zhaoyun ,   Tsinghua University, Wen Mengyang ,   Tsinghua University, Zheng Xinqian ,   Tsinghua University
Published: February 2024

Adaptive cycle engine (ACE) with multi-stream, modulated bypass ratio, and high-thrust/high-efficiency mode provides the capability of multiple mission adaptation for the next-generation aviation propulsion system. The low-fidelity zero-dimensional (0D) performance simulation method is commonly adopted in conventional engines such as turbofan and turbojet. However, it is hard to accommodate well to ACE with complex variable geometry schemes and strong interaction between components. This paper presents an efficient multi-fidelity simulation approach, often referred to as component zooming, for predicting the performance of ACE with the three-stream configuration. The one-dimensional (1D) mean-line models of the adaptive fan and low-pressure turbine (LPT) are integrated into the 0D ACE model by the iteratively-coupled method. The performance predicted by the multi-fidelity ACE models with different component zooming strategies is compared. The maximum deviations of thrust, specific fuel consumption, turbine inlet temperature, and bypass ratio between the 0D/1D Adaptive Fan/1D LPT coupled model and 0D ACE model are -10.8%, -4.4%, -5.4% (-75K), and 1.6%, respectively, which are considerable and non-negligible for the application in the design stage of ACE. The computing time of all the multi-fidelity models is less than 2 minutes. The effects of the key aerodynamic parameters of the adaptive fan and LPT on the engine performance are also evaluated. The proposed approach provides a generic and efficient solution for multi-fidelity ACE performance prediction with acceptable computing resource requirements and time cost, which is applicable in the engine conceptual and preliminary design stage.
Study of a High-Pressure Ratio Centrifugal Compressor with a Wedge Diffuser and a Pipe Diffuser
Authors:   School of Power and Energy, Northwestern Polytechnical University, Liu Jun-nan , Huang Xiuquan ,   School of Power and Energy, Northwestern Polytechnical University
Published: February 2024

A high-performance diffuser is crucial for a high-pressure ratio centrifugal compressor, as it dominates the flow downstream of the impeller. Pipe diffusers have been proved to be effective for high-pressure ratio centrifugal compressors. To understand the performance and flow mechanisms of pipe diffusers, an 8:1 pressure ratio centrifugal compressor is selected and a comparative study of compressor stages with a pipe diffuser and its original wedge diffuser was carried out using numerical simulations. At the design speed, the compressor with the pipe diffuser presents a better performance (lower total pressure loss, higher static pressure recovery and stable flow range) over the whole speedline than that with the wedge diffuser. The peak efficiency of the compressor with the pipe diffuser is 2.4 percentage points higher than that with the wedge diffuser. Compared with the wedge diffuser, the special scalloped leading edge of the pipe diffuser was found to reduce or even eliminate the flow distortion from upstream of the diffuser throat, which is beneficial to suppress the downstream flow separation.
Numerical Investigation of the Potential of Multi-Row Optimization of an Axial Compressor Stage with a Tandem Vane Stator
Authors:   Technical University of Munich, Giannini Samuele , von Jeinsen Philipp ,   Technical University of Munich, Straccia Mattia ,   Technical University of Munich, Banik Sagnik ,   Technical University of Munich, Gümmer Volker ,   Technical University of Munich
Published: February 2024

In the published literature, there are few examples of axial compressors designed with tandem vanes, aimed to increase the maximum loading of the machine. It appears that the advantages of employing tandem vanes are overruled by additional problems arising in real compressor applications. Phenomena such as the increase in endwall and secondary losses prevent tandem vanes from being widely employed in current commercial engine designs. In this work, the aerofoil geometries of the IGV, rotor, and the shrouded tandem stator of a highly loaded axial compressor stage are improved in a combined optimization, using the potential of this configuration in a one-and-a-half-stage environment. The redesigned compressor stage shows performance improvements in total pressure ratio of each vane and isentropic efficiency of the one-and-a-halfstage. The optimized stage is extended to the three-and-a-half-stage configuration of the machine, confirming and extending the benefits of the optimized geometries with an increase in stage work coefficient of 3% and in stage isentropic efficiency of up to 0.76%. Starting from these results, the authors widen the content of this work to provide a better understanding and a solid background on the design of axial compressor stages with tandem vanes, highlighting their potential benefits in multi-stage environments.
A novel approach to aeroengine performance diagnosis based on physical model coupling data-driven using low-rank multimodal fusion method
Authors:   Department of Aeronautics & Astronautics, Fudan University, Wang Zepeng , Wang Xizhen ,   Department of Aeronautics & Astronautics, Fudan University, Wang Ye ,   Department of Aeronautics & Astronautics, Fudan University, Zhao Bokun ,   Department of Aeronautics & Astronautics, Fudan University, Zhaoa* Yongjun ,   Department of Aeronautics & Astronautics, Fudan University
Published: February 2024

Aeroengine health assessment is crucial to ensure flight safety and reliability. Traditionally, it involves diagnosing the performance of the aeroengine gas path. However, due to the complexity of operating conditions, non-linear performance, and the coupling of gas path performance fault characteristics, determining the aeroengine health condition directly from engine monitoring information is challenging, especially with insufficient sensor data. To tackle these challenges, a novel digital twin method for aeroengine performance diagnosis was proposed. This method utilizes data-driven and performance models, employing low-rank multimodal fusion. By digitizing the physical system or process through mathematical models and simulation technology, this approach offers distinct advantages compared to previous methods based solely on models or data. At the aeroengine component level, an adaptive model was employed, and the data-driven model was constructed using flight data. Support vector machines were utilized for gas path fault classification. The engine digital twin was created through low-order multimodal fusion. The results demonstrate that the proposed method achieves excellent diagnostic accuracy under both steady and transient conditions. It can be utilized to enhance engine performance monitoring and evaluation, as well as improve the reliability, availability, and efficiency of the engine.
Multi-fidelity aerodynamic performance modeling of supercritical carbon dioxide compressor
Authors:   Science and Technology on Thermal Energy and Power Laboratory + Wuhan Second Ship Design and Research Institute, Ma Can , Lao Xingsheng ,   Science and Technology on Thermal Energy and Power Laboratory + Wuhan Second Ship Design and Research Institute, Gou Jinlan ,   Science and Technology on Thermal Energy and Power Laboratory + Wuhan Second Ship Design and Research Institute, Zhang Kelong ,   Science and Technology on Thermal Energy and Power Laboratory + Wuhan Second Ship Design and Research Institute, Wang Wei ,   Science and Technology on Thermal Energy and Power Laboratory + Wuhan Second Ship Design and Research Institute
Published: February 2024

Fast and accurate prediction of compressor aerodynamic performance is required in the system design and analysis of the supercritical carbon dioxide(S-CO2) power cycle. However, the S-CO2 compressor typically operates at an inlet fluid state close to the fluid critical point for optimal cycle efficiency. As the fluid parameters vary significantly near the critical point, accurate compressor modeling is more challenging with current meanline models, considering lack of adequate experimental data to validate various empirical correlations. This work proposed a multi-fidelity model for the aerodynamic performance prediction of the S-CO2 compressor, which enhances the meanline model with limited reliable experimental data or high-fidelity numerical data. The advantage of low cost with the meanline model is retained in the current multi-fidelity model, while a cheap surrogate model is constructed to improve the accuracy. The model is applied to the aerodynamic performance prediction of typical S-CO2 compressor cases.
Darmstadt Open Test Case: Experimental Investigation of Forced Response Phenomena in a Transonic Compressor Stage
Authors:   Technical University of Darmstadt, Klausmann Fabian , Schmidt Benedikt ,   Technical University of Darmstadt, Kilian Nicklas ,   Technical University of Darmstadt, Spieker Daniel ,   Technical University of Darmstadt, Schiffer Heinz-Peter ,   Technical University of Darmstadt
Published: February 2024

The modular compressor at the Transonic Compressor Darmstadt test facility at Technical University of Darmstadt enables investigations of prototype BLISK rotors in single or 1.5-stage setups, operating at high-speed conditions. Within the framework of the European funded research project ARiAS (Advanced Research into Aeromechanical Solutions), forced response blade vibration phenomena and underlying fluid-structure-interaction are investigated. For this, the Darmstadt Open Test Case is enhanced with new rig hardware and equipped with additional steady and unsteady instrumentation to perform extensive aerodynamic and aeromechanical tests. To excite a distinct engine order, a variable wake generator module is applied upstream the rotor BLISK containing 3-16 equally spaced symmetric NACA airfoils. One goal is to experimentally characterize the resulting flow features and determine the impact of wake forcing and rotor tip-clearance on blade vibration and aero-damping by performing a parameter study of various configurations and operating conditions. This paper comprises an overview of the ARiAS compressor stage setup, applied instrumentation and performed measurements. It emphasizes the substantial aerodynamic variations induced by different excitation features, while simultaneously highlighting the inherent independence of the measured system damping from these variations across three fundamental resonance crossings.