bluuebunny/crossref_metadata_2025_split huggingface dataset:
Review of Non-Fluorinated Durable Water Repellent and Stain-Resistant Materials and Their Future development
Authors: Guo Wenzhuo , Li Zhiyun , Ma Zixi 
Published: May 2021

AbstractMaterials with superhydrophobic surfaces have significant values in industrial applications for the reason that these materials usually has the abilities of self-cleaning and stain-resisting. Currently, most superhydrophobic materials are fluorinated ones because fluorinated groups contribute to decreasing the surface energy and surface tension of materials. Nevertheless, toxicity of fluorinated materials prevents them from being widely used in some industrial areas. Thus, this paper aims to have a review of methods used to fabricate non-fluorinated materials with superhydrophobic surfaces. This work introduces both the advantages and disadvantages of fluorinated materials and displays the reasons why materials can be superhydrophobic. In addition, hierarchical structures and re-entrant structures are shown in this passage and methods of making these structures are listed. Besides, this paper presents some methods to fabricate structures which contribute to superhydrophobization. Furthermore, some non-fluorinated materials are listed and their abilities of repelling water and stains are displayed, consisting of silanes, organic materials, and inorganic materials. At last, this paper illustrates current limitation of non-fluorinated materials and their future developments.
Noise mechanisms in a radial fan without volute
Authors: Sanjosé Marlène , Hub Sandra , Lörcher Frieder , Moreau Stéphane 
Published: May 2021

Abstract
The noise emission of a large radial fan with 7 backward curved blades is investigated. When decreasing the flow rate, the broadband levels below 1 kHz increase and the tones decrease, and a broad hump appears at about 80% of the BPF. The present numerical investigation aims at identifying the mechanism responsible for the broadband hump in the spectra. The configuration is simulated using the Lattice Boltzmann PowerFLOW solver for four flow-rate conditions. The low flow-rate condition is run longer to achieve statistical convergence at low frequencies. The simulations capture reasonably well the acoustic spectra and in particular the broadband hump at lower flow rate. The flow in the fan shows an unsteady flow detachment in some blade passages shed from the leading edge of the blade, while other blade passages experienced a fully detached flow along the whole blade chord. A spectral proper orthogonal decomposition is applied to identify the modal structures of the flow responsible for this mechanism. Several azimuthal modes are obtained from the decomposition for the different frequencies in the acoustic spectra. In addition an axial acoustic mode in the fan bowl is found at a frequency in the broadband hump.
Towards the definition of a benchmark for low Reynolds number propeller aeroacoustics
Authors: Casalino D. , Grande E. , Romani G. , Ragni D. , Avallone F. 
Published: May 2021

Abstract
Experimental and numerical results of a propeller of 0.3 m diameter operated in quiescent standard ambient conditions at 5000 RPM and axial velocity ranging from 0 to 20 m/s and advance ratio ranging from 0 to 0.8 are presented as a preliminary step towards the definition of a benchmark configuration for low Reynolds number propeller aeroacoustics. The corresponding rotational tip Mach number is 0.231 and the Reynolds number based on the blade sectional chord and flow velocity in the whole radial and operational domain ranges from about 54000 to 106000. Force and noise measurements carried out in a low-speed semi-anechoic wind-tunnel are compared with scale-resolved CFD and low-fidelity numerical results. Results identify the experimental and numerical challenges of the benchmark and the relevance of fundamental research questions related to transition and other low Reynolds number effects.
Influence of the rotor blade aspect ratio on the performance of an axial fan
Authors: Theis A , Böhle M 
Published: May 2021

Abstract
An axial fan with four different number of blades for the rotor is investigated. In this contribution varying the blade aspect ratio means the number of blades is changed while every other dimensionless design parameters and the design point are kept constant. By varying the blade aspect ratio, the length of the blades alters and as a result the Reynolds number which is related to the chord length of each blade is changed as well. The considered Reynolds numbers are lying between 2.38 × 105 and 7.13 × 105. For the stator the blade aspect ratio as well as the spacing ratio are the same during the investigation.
For comparison and validation both numerical and experimental investigations are performed. For the numerical investigations, due to the low Reynolds numbers the k-ω-SST transition model with the intermittency function is applied. Transient simulations are carried out. The experimental investigations are performed a pipe test bench. The results are compared in terms of performance differences for part load, overload and design conditions. The flow structure in the rotor passages is visualized and compared using the numerical results to show the influence of the blade aspect ratio on the performance.
Experimental study of a centrifugal compressor with two successive and counter-rotating impellers
Authors: Nguyen Van-Thang , Danlos Amélie , Paridaens Richard , Ravelet Florent , Deligant Michael , Khelladi Sofiane , Bakir Farid 
Published: May 2021

Abstract
In many industries, reducing the size of the compression system represents a significant goal for designers. In fact, increasing the power density of the compressor actually means lowering production costs. The chief purpose of this study is to compare, in terms of aerodynamic performances, a centrifugal compressor consisting of an impeller and a volute, to an innovative concept based on the principle of two successive impellers and designed to work in counter-rotation. To simplify the experimental research in this study, the volute of the conventional compressor is maintained for the new design. The conventional impeller has been replaced by two successive impellers having the same meridian profile, and whose diameter of the rear impeller is identical to that of the conventional impeller. The impellers design of the counter-rotation stage was carried out granting to an approach proposed here. The numerical results underline the advantage of the innovative compressor, in terms of power density, compared to the conventional design. The numerical forecasts also agree significantly with the results of experimental tests got on a test bench exclusively designed for compressors. Experimental optimization of the rotational speed ratio of the two counter-rotating impellers has demonstrated the possibility of increasing the compression ratio and efficiency over a wide range of flow.
Effects of some settings of rotational-molding process on the aeromechanical performance of an axial fan.
Authors: Dang Vu-Dinh , Danlos Amélie , Pereira Michaël , Shirinbayan Mohammadali , Ravelet Florent , Bakir Farid , Tcharkhtchi Abbas 
Published: May 2021

Abstract
The study purposes to establish the influence of some settings of the conventional rotational-molding process on the aeromechanical performance of a hollow-blade axial fan. It is recognized that the surface state quality, the material characteristics and the blades design have an effect on the performances of the turbomachines. The use of conventional rotational-molding is an innovative method well suited for achieved hollow-blade fans, reduced cost and relatively easy manufactured. In the present work the material employed represents one grade of linear low-density polyethylene (LLDPE-3200 natural, supplied by “C4-Polymers Company”). The variables of the process studied attend the initial mass of polyethylene powder, the oven temperature and the heating time. For comparisons, a fan of similar geometry machined in an aluminium block serves additionally as a reference. The results show an optimal choice of the settings of the manufacturing process is necessary to achieve the desired aeromechanical performances for this fan.
Aerodynamic design optimization of a bellmouth shaped air intake for jet engine testing purposes and its experiment based validation
Authors: Sevinç Koray 
Published: May 2021

Abstract
Jet engine ground tests are carried out with bellmouth shaped air intakes in order to measure the mass flow rate and the inlet flow quantities while supplying the engine an undisturbed flow. Although there are a variety of design standards and academic guidelines for the design of bellmouths, they can be designed to reach a lower total pressure loss coefficient, a less disturbed radial velocity profiles for the engine and a less thickened boundary layer at the engine inlet. This enhanced design can be achieved with the help of optimization algorithms and computational fluid dynamics (CFD) computations thanks to the increasing average computational power and simplicity of the flow problem. In this study, a genetic algorithm based optimization method and a RANS solver under a commercial software platform are applied to find a bellmouth design with less loss and less disturbed flow. An elliptical bellmouth lip profile with a linear extension part is defined with parametrization and a wide range of parameter space is investigated during the design work. Optimum design candidates are presented comparatively regarding the design purpose. The selected design candidate is produced and tested for CFD validation.
Assessment of single passage simulations for the aeroelastic stability of a multistage centrifugal compressor
Authors: Placzek Antoine 
Published: May 2021

Abstract
In this paper, the aeroelastic flutter stability of an impeller is investigated numerically with single passage and full annulus URANS simulations carried out on one side on a single stage configuration including a strut and the impeller and on the other side on a multistage configuration in which two additional diffusers are considered downstream. The robustness of single passage simulations relying on the use of multiple frequency phase-lagged boundary conditions is put to the test especially in the case of the multistage configuration for which both blade passage and aeroelastic effects have to be taken into account. Comparisons between single passage simulations on the single and multistage configurations indicate that the impeller-diffuser interaction acts locally on the impeller fluid-structure interface and has only little effect on the generalized aerodynamic forces. Full annulus simulations have also been carried out to assess the accuracy and efficiency of single passage simulations which introduce additional hypotheses of periodicity in the flow. Full annulus simulations are competitive in terms of wall clock since the convergence to the periodic state is faster than with single passage simulations involving the Fourier approximation of the flow field.
Sealing Performance of a Turbine Rim Chute Seal Under Rotationally-Induced Ingestion
Authors: Revert Anna Bru , Beard Paul F. , Chew John W. , Bottenheim Sebastiaan 
Published: May 2021

Abstract
This study focuses on the sealing capability of a turbine rim seal subject to hot gas ingestion driven purely by the rotor disc pumping effect rather than that induced by mainstream features such as vane and rotor blade passing. The aim is to provide useful data for conditions in which rotation dominates, and to clarify the flow physics involved in rim sealing. Experimental measurements of sealing effectiveness for a chute seal are presented for the first time without and with an axial, axisymmetric mainstream flow external to the seal. The test matrix covers a range of rotational Reynolds number, Reø, from 1.5x106 to 3x106, and non-dimensional flow rate, Cw, from 0 to 4x104 with the mainstream flow (when present) scaled to match engine representative conditions of axial Reynolds number, Reax. Results from steady pressure and gas concentration measurements within the rotor-stator disc cavity and the rim seal gap are presented and compared to published data for other seal designs. Sealing performance of the chute seal is somewhat similar to that of axial clearance seals with the same minimum clearance.
Influence of meridional plane shape on performance and internal flow of high head contra-rotating small hydroturbine
Authors: Hosotani Takuji , Shigemitsu Toru , Kawaguchi Yuki , Inamoto Takuya , Ishiguro Takeru , Nan Ding 
Published: May 2021

Abstract
It is requested that the hydroturbine be a small size and have high performance. Therefore, we adopted contra-rotating rotors, which can be expected to achieve radial compactification and high performance. However, a conventional contra-rotating rotor was composed of two axial flow rotors, so it had a specification suitable for high flow rate and low head. In order to achieve small hydroturbine suitable for low flow rate and high head, we propose a new type of contra-rotating rotors, which are composed of a hybrid rotor and a centrifugal rotor. In the present paper, we focus on the meridional plane shape at the connection between the front rotor and the rear rotor of the hydroturbine composed of these rotors as a first step of this research, and investigate performance by the numerical analysis. As a result, we clarified that the relationship between the performance and internal flow when the blade width at the connection between the front rotor and the rear rotor changed.
Comparative Study on Starting Characteristics of Turbines for Wave Energy Conversion
Authors: Takao M , Kanetsuki K , Alam M M A , Okuhara S , Kinoue Y 
Published: May 2021

Abstract
Wells and impulse turbines for bi-directional airflow have been proposed as typical turbines for wave energy conversion. Each of them has some advantages and disadvantages. In recent years, the authors have proposed Wells turbine with booster and a counter-rotating impulse turbine for bi-directional airflow in order to overcome their drawbacks. In this study, the starting characteristics of four types of turbines for bi-directional airflow were compared by conducting a CFD analysis under a steady flow condition.
Transport of heat and material properties in continuous casting of steel
Authors: Holl Helmut J. , Simon Gottfried 
Published: May 2021

Abstract
Liquid steel solidifies within a containment of a continuous casting machine and moves in axial direction as the solidified shell is withdrawn towards the end of the machine. A mechanical model for computing the deformation of the solidifying steel in the roll containment is developed based on the beam theory and on a ferro-static pressure load. The material properties of the steel at high temperatures result from high temperature constitutive equations including creep for the solidified shell between the rolls. The temperature distribution within the solidified shell is computed based on the thermal boundary conditions as in the secondary cooling zone water is spread onto the surface of the steel shell and heat is removed. The solidified steel shell thickness increases along the machine containment up to the point of total solidification. A suitable discretization of the region by the finite beam elements is used to get a suitable mechanical model. The ferro-static pressure acts inside of the solidified shell and causes some bulging of the shell between the roll containment. As there is a slow axial motion of the solidifying shell the numerical modeling of the transport e.g. of heat and of the creep strain, which is computed in each time step, has to be as accurate as possible as a lot of time steps are necessary. Different numerical strategies have been analysed with respect to the accuracy of the computation results.
Challenges in 3D CFD Modelling of Rotary Positive Displacement Machines
Authors: Kovacevic Ahmed , Rane Sham 
Published: May 2021

Abstract
The use of Computational Fluid Dynamics (CFD) and Computational Continuum Mechanics (CCM) for analysis of rotary positive displacement machines is exponentially increasing which was mostly allowed by the development of methods for generating numerical grids of complex domains within the machines. However there are several challenges with the commercial CFD/CCM codes which are preventing generic use of CFD. These are conservativeness of spatial discretisation caused by the inappropriate grid generation, numerical instabilities and dissipations caused by misalignments and application of inappropriate discretisation of equations and the speed and accuracy of multiphase models used in CFD of positive displacement machines.
In this paper the authors will review methods used for modelling of rotary positive displacement machines and challenges which developers and users of these methods face. The paper will also offer some solutions and directions for resolving these issues.
Discussion of Numerical Methods used in Positive Displacement Comprehensive Mechanistic Models: Case Study using the Z-Compressor
Authors: Bradshaw Craig R , Ziviani Davide , Groll Eckhard A 
Published: May 2021

Abstract
Comprehensive mechanistic models have been widely used for simulating positive displacement (PD) compressors or expanders. Such models are based on a thermodynamic analysis of generic control volumes that describe the working chambers. The thermodynamic analysis results in a set of non-linear ordinary differential equations (ODEs) that describe conservation of mass and energy. The derived ODEs are used to predict the evolution of the thermodynamic properties of the working fluid with respect to crank angle or time. The solution scheme of a mechanistic model involves different layers of solvers that handle the step-by-step integration, the cycle-to-cycle continuity as well as the overall energy balance. Since most of the PD machines feature multiple control volumes that merge or split (e.g. scroll-type) or wrap-around a rotor (e.g. screw-type) the integration scheme faces challenges due to the stiffness of the equations or discontinuities in the control volume definition.
In this paper, a discussion of different integration schemes and numerical considerations are proposed that are applied to a novel compressor called the z-compressor which presents a high-degree of intrinsic stiffness. A simplified comprehensive model is developed which is validated against experimental mass flow rate data for a prototype compressor with an average model-predicted error of less than 2%. This model is used to explore the differences in two ODE solvers from the ODE suite in MATLAB, (ODE15s, and ODE113). These results are further compared against an existing, simplified, Z-compressor model developed in PDSim which uses an explicit, lower order, solver the Adaptive Runge-Kutta (RKF). The results suggest that the semi-implicit solver (ODE15s) provides an efficient means for stepping through the compression process ODEs compared to the explicit solvers.
Energy balance analysis for a canned motor pump used for heat supply system
Authors: Song Xueyi , Yu Weiping , Pan Xiaohui , Luo Xianwu 
Published: May 2021

Abstract
A canned motor pump is widely used for transporting the liquids without leakage. In this work, the pump is applied for heat supply system. For this application, between the rotor and stator for cooling the canned motor there is a circulating flow, which will flow back in the pump passage with higher temperature, and bring the mixing of the liquid having different temperature between the main stream and the circulating flow. The steady state internal flow has been investigated for the pump, and the pump hydraulic performance has been compared with the experimental data. With the consideration of both mechanical energy and internal energy as the effective energy increment of the working fluid, an efficiency assessment is proposed for a canned motor pump. The proposed efficiency shows the same tendency as hydraulic efficiency, and is more understandable compared with that of the conventional method. The present results indicate that the proposed method of evaluating the efficiency of the canned motor pump can reasonably depict the energy balance inside the whole canned motor pump. Further, the introduction of circulating flow is helpful to predict the internal flow and heat transfer for the canned motor pump in numerical simulation with better accuracy. The present study is helpful for both development and application of high performance canned motor pump for various industries.
Effect of axial offset of rotor on thrust characteristics of a centrifugal pump
Authors: Takamine T , Nakano S , Watanabe S , Watanabe H 
Published: May 2021

Abstract
To ensure the reliability of multi-stage centrifugal pumps, the prediction of axial thrust is an important issue for the design of balancing device and selection of thrust bearing. However, it is known that the fluid forces acting on rotor could be sensitively affected by the geometrical relations between rotor and stator especially at the low flow rate. Among them, the effect of axial offset of rotor has not been studied sufficiently though the axial offset is easily caused by accumulation of manufacturing tolerances and assembling errors. In this study, experimental/numerical investigations on the effect of axial rotor offset in a final stage model of a three-stage centrifugal pump are carried out. The axial offset is intentionally given to shaft system to the both of discharge/suction side. As a result, the axial thrust is significantly affected by the axial offset in the flow rate range below 50% of the design. It is shown by CFD analysis that this effect of axial offset is caused by the interaction between the back flow from the diffuser and the main flow.
Analysis of Morton Effect Induced Vibration based on Transfer Function Model: Influence of L/D ratio of Journal Bearing and Rotational speed
Authors: Suzuki Takafumi , Chiba Jotaro , Yabui Shota , Tomimatsu Shigeyuki , Inoue Tsuyoshi 
Published: May 2021

Abstract
The Morton effect is the vibration phenomena that occur due to a thermal imbalance in the oil film in the journal bearing. In previous studies, the qualitative evaluation was performed based on theoretical modeling and numerical simulation. On the other hand, authors proposed that the characteristic of the journal bearing was considered as a proportional differential controller from a control engineering point of view. In the proposed model, the vibration due to the Morton effect can be evaluated based on the transfer function models. The proposed model is based on frequency characteristics identified from the experimental data directly, therefore, the model can be easily applied to the actual rotating machineries. The authors focus this study on applying the proposed method to the actual design, and investigated the relationship of the parameters of the transfer function between the L/D ratio and rotating speed. The relationship indicates the degree of influence of the L/D ratio and rotating speed to the vibration due to the Morton effect. The author measured the vibration by arbitrarily setting the L/D ratio, and analyzed the influence to the vibration due to the Morton effect based on the transfer function model. As a result, the author was able to predict the influence of the bearing L/D and rotating speed on the Morton effect.