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Lead alloy is used as coolant in Lead-based cooled Fast Reactor (LFR). The natural characteristics of lead alloy are combined with the simple structural design of LFR. This constitutes the inherent safety characteristics of LFR. The main work of this paper is to take the main coolant pump (MCP) in the lead-cooled fast reactor (LFR) as the research object, and to study the flow pattern distribution of the internal flow field under the reverse rotation pump condition, the reverse rotation positive-flow braking condition and the reverse rotation negative-flow braking condition. In this paper, the double-outlet volute type and the space guide vane are selected as the potential designs of the CLEAR-I MCP. In this paper, the CFD method is used to study the potential reverse accident of the MCP. It is found that the highest flow velocity in the impeller appears at the impeller outlet, and the Q-H curves of the two design programs basically coincide. The space guide vane type MCP has better hydraulic performance under the reverse rotation positive-flow condition, the Q-H curves of the two designs gradually separate with increasing flow rate, and the maximum flow velocity inside the space guide vane type MCP is obviously lower than that of the double-outlet volute type. For the reverse rotation test of MCP, only the condition of the forward rotating pump of the main coolant pump is tested and verified. For the simulation of the MCP in LBE medium, it proved that the turbulence model and basic settings selected in the simulation are reliable.

The instantaneous acceleration affects the performance of the water-jet pump obviously. Here, based on the user-defined function, the method to simulate the inner flow in water-jet pumps under acceleration conditions was established. The effects of two different acceleration modes (linear acceleration and exponential acceleration) and three kinds of different acceleration time (0.5s, 1s and 2s) on the performance of the water-jet pump were analyzed. The results show that the thrust and the pressure pulsation under exponential acceleration are lower than that under linear acceleration at the same time; the vapor volume fraction in the impeller under linear acceleration is 27.3% higher than that under exponential acceleration. As the acceleration time increases, the thrust gradually increases and the pressure pulsation amplitude at the impeller inlet and outlet gradually decreases, while the law of pressure pulsation is the opposite at the diffuser outlet. The main frequency of pressure pulsation at the impeller outlet is different under different acceleration time. The research results can provide some reference for the optimal design of water-jet pumps.

In order to research the fluid-induced force of centrifugal pump impeller with compound whirling, based on the N-S equations, the RNG k-e turbulence model is applied to simulate the low specific speed centrifugal pump under eccentric assembly condition. The effects of different flow rates, impeller eccentricities and whirl ratios on the fluid-induced force of impeller were investigated. Finally, the fitting models of fluid-induced force with compound whirl were obtained by least square method (LSM). The results imply that the calculated results considering the impeller eccentricity are closer to the experimental data than those without considering the eccentric whirl. In addition, the extremum value of fluid-induced force of impeller has a significant positive correlation with the impeller eccentricity. With the increase of flow rate, the fluid-induced force is non-monotonic. The whirl ratio can change the numbers of peak and valley of fluid-induced force, and the nonlinear fitting model of fluid-induced force using LSM presents high precision. This study can provide important references for the design and fluid-structure interaction (FSI) vibration of centrifugal pump.

An annular linear induction electromagnetic pump (ALIP) which has a developed pressure of 0.76 bar and a flow rate of 100 L/min is designed to analysis end effect which is main problem to use ALIP in thermohydraulic system of the prototype generation-IV sodium-cooled fast reactor (PGSFR). Because there is no moving part which is directly in contact with the liquid, such as the impeller of a mechanical pump, an ALIP is one of the best options for transporting sodium, considering the high temperature and reactivity of liquid sodium. For the analysis of an ALIP, some of the most important characteristics are the electromagnetic properties such as the magnetic field, current density, and the Lorentz force. These electromagnetic properties not only affect the performance of an ALIP, but they additionally influence the end effect. The end effect is caused by distortion to the electromagnetic field at both ends of an ALIP, influencing both the flow stability and developed pressure. The electromagnetic field distribution in an ALIP is analyzed in this study by solving Maxwell's equations and using numerical analysis.

A model has been developed to characterize the cavitation phenomenon in dredging centrifugal pumps. The operating parameters of a cutter type dredger: swing speed, dredging depth, and inclination, impeller rpm, as well as slurry characterizations such as density and velocity, are introduced, to determine how they influence the operation of the dredge pump. The geometric characterization of the hydraulic transport system of the dredger was performed. With the dredge operationaĺs parameters, along with the geometric characterization, the pump is modeled in CFD turbomachinery software. To validate the operational points, the CFD model considers the RNG k-ε model and the cavitating-multiphase flow. Through the central composite experiment design, the operating conditions range of the dredger is determined, in which the pump can operate and cavitate. This allows validating the model for different operational points. Finally, multiple regression shows the influence of each of the variables in the response obtained. Furthermore, the regression allows an understanding that operating conditions of the dredger must be adjusted to mitigate the phenomenon of cavitation in the dredging process. Keywords: Cavitation, Centrifugal pump, CFD, Dredging, Slurry

In a total flow geothermal system, the two-phase turbine can generate output power and recover fresh water for the water-deficient area. The performance of the two-phase turbine under various working conditions is significantly affected by operation parameters of the geothermal system. This paper presented performance evaluation methods of two-phase turbines, including one-dimensional (1D) method, two-dimensional (2D) method and three-dimensional (3D) method. The 1D method was a fast iteration approach and could reflect average flow parameters along the impeller channel. The 2D method included nonuniform effects in the rotational direction and the 3D method could derive the complete 3D flow in the channel using CFD methods. The three models were validated with experimental results under various rotational speeds. Compared with the 3D method, the 1D method and the 2D method could significantly reduce computational time. The performance of the two-phase reaction turbine was evaluated under various working conditions. A correction method based on 1D and 3D results was proposed to generate the performance map and evaluate the influence of operation parameters of the geothermal system on the turbine performance. Proposed methods and analysis can be widely used in the design, selection and operation of two-phase reaction turbines for various thermal systems.

Roller compaction followed by milling of the generated ribbons is a typical dry granulation route. It is desirable to be able to predict the size distribution of the granules exiting the mill based on the ribbon properties and mill operational conditions. Two DEM-PBM approaches for predicting this size distribution are compared; a direct approach where the size distribution is experimentally determined, and an indirect approach where the successive change in size distribution due to each stressing event is determined mathematically by the PBM. The experimental component of the direct approach assumes shear deformation to be the dominant breakage mechanism. This approach provides a reasonable agreement to experimental data, though the influence of mill parameters is not experimentally tested. When considering breakage to be driven by impact, the indirect approach predicts the correct magnitude of fines generation, though incorrectly predicts the fine fraction to increase with impeller speed. When abrasion is assumed to be the dominant breakage mechanism, the indirect approach suggests the same trend, though with a less pronounced effect of impeller speed and a closer agreement to experimental data. Prediction accuracy is expected to improve by considering distributions of stressing conditions and material strength, the latter being explicitly captured in the experimental component of the direct approach. Furthermore, the direct approach accounts for the variable loading conditions of the fragments in the mill.

Cavitation caused by insufficient suction is a major factor that influences the life of aircraft pumps. Currently, pressurizing the tank can solve the cavitation problem under steady large-flow conditions. However, this method is not always effective under transient conditions (from zero flow to full flow in a very short time). Moreover, to apply and design other measures, such as a boost impeller, the suction dynamics during the transient period must be investigated. In this paper, a novel approach based on the pressure wave propagation theory is proposed for predicting the inlet pressure of an aircraft pump under transient conditions. First, a dynamic model of a typical aircraft pump is established in the form of differential equations. Then, the transient flow model of the inlet line is described using momentum and continuity equations, and the governing equations are discretized by the method of characteristics and the finite difference method. The simulated results are in good agreement with the results from verification tests. Further simulation analysis indicates that the wave velocity and transient time may influence the inlet and reservoir pressure as well as the size of the inlet line. Finally, solutions for upgrading the inlet pressure are discussed. These solutions provide guidelines for designing inlet installations. Keywords: Aircraft hydraulic pump, Boost impeller, Inlet pressure, Method of characteristics, Transient condition, Wave propagation

The AP1000 reactor coolant pump is a vertical shielded-mixed flow pump, is the most important coolant power supply and energy exchange equipment in nuclear reactor primary circuit system, whose steady-state and transient performance affect the safety of the whole nuclear island. Moreover, safety demonstration of reactor coolant pump is the most important step to judge whether it can be practiced, among which software simulation is the first step of theoretical verification. This paper mainly introduces the fluid-solid coupling simulation method applied to reactor coolant pump, studying the feasibility of simulation results based on workbench fluid-solid coupling technology. The study found that: for the unsteady calculations of the pure liquid media, the average head of the reactor coolant pump with bidirectional fluid-solid coupling decreases to a certain extent. And the coupling result is closer to the real experimental value. The large stress and deformation of rotor under different flow conditions are mainly distributed on impeller and idler, and the stress concentration mainly occurs at the junction of front cover plate and blade outlet. Among the factors that affect the dynamic stress change of rotor, the pressure load takes a dominant position. Keywords: Reactor coolant pump, Bidirectional fluid-solid coupling, Safety demonstration, Steady state condition, Nomenclature

Selecting the optimal machining parameters for impeller surface is a challenging task in the automatic manufacturing industry, due to its free-form surface and deep-crooked flow channel. Existing experimental methods require lots of machining experiments and off-line tests, which may lead to high machining cost and low efficiency. This paper proposes a novel method of machining parameters optimization for an impeller based on the on-machine measuring technique. The absolute average error and standard deviation of the measured points are used to define the grey relational grade for reconstructing the objective function, and the complex problem of multi-objective optimization is simplified into a problem of single-objective optimization. Then, by comparing the values of the defined grey relational grade in a designed orthogonal experiment, the optimal combination of the machining parameters is obtained. The experiment-solving process of the objective function corresponds to the minimization of the used errors, which is advantageous to reducing the machining error. The proposed method is efficient and low-cost, since it does not require re-clamping the workpiece for off-line tests. Its effectiveness is verified by an on-machine inspection experiment of the impeller blade. Keywords: Grey relational grade, Impeller surface, Multi-parameters optimization, On-machine measuring, Orthogonal experiment

The current study was to understand how process variables of high shear wet granulations affect physical properties of granules and tablets. The knowledge gained was intended to be used for Quality-by-Design based process design and optimization. The variables were selected based on the risk assessment as impeller speed, liquid addition rate, and wet massing time. Formulation compositions were kept constant to minimize their influence on granules properties. Multiple linear regression models were built providing understanding of the impact of each variable on granule hardness, Carr's index, tablet tensile strength, surface mean diameter of granules, and compression behavior. The experimental results showed that the impact of impeller speed was more dominant compared to wet massing time and water addition rate. The results also revealed that quality of granules and tablets could be optimized by adjusting specific process variables (impeller speed 1193 rpm, water spray rate 3.7 ml/min, and wet massing time 2.84 min). Overall desirability was 0.84 suggesting that the response values were closer to the target one. The SEM image of granules showed that spherical and smooth granules produced at higher impeller speed, whereas rough and irregular shape granules at lower speed. Moreover, multivariate data analysis demonstrated that impeller speed and massing time had strong correlation with the granule and tablet properties. In overall, the combined experimental design and principal component analysis approach allowed to better understand the correlation between process variables and granules and tablet attributes., Graphical abstract Image, graphical abstract

Power generators and chemical engineering compressors include heavy and large centrifugal impellers. To produce these impellers in high-speed machining, a 4½-axis milling machine (or a 4-axis machine plus an indexing table) is often used in the industry, which is more rigid than a 5-axis milling machine. Since impeller blades are designed with complex B-spline surfaces and impeller channels spaces vary significantly, it is more efficient to use multiple cutters as large as possible to cut a channel in sections and a blade surface in patches, instead of only using a small cutter to machine a whole blade and a channel. Unfortunately, no approach has been established to automatically calculate the largest diameters of cutters and their paths, which include the indexing table angles. To address this problem, an automated and optimization approach is proposed. Based on the structure of a 4½-axis machine, a geometric model for a cutter gouging/interfering the impeller is formulated, and an optimization model of the cutter diameter in terms of the indexing table angle is established at a cutter contact (CC) point on a blade surface. Then, the diameters of the tools, their orientations, and the indexing table angles are optimized, and each tool’s paths are generated for machining its corresponding impeller section. As a test, an impeller is efficiently machined with these tools section by section; thus, this approach is valid. It can be directly used in the industry to improve efficiency of machining centrifugal impellers. Keywords: Automated path generation, 4½-Axis CNC machining, Centrifugal impeller machining, Cutter diameter optimization, Sectional machining

Quartz, the second most abundant mineral in the earth’s crust, is a gangue mineral in practically every flotation process. Coarse quartz flotation has been a long standing problem in various mineral processing plants to reduce milling cost and increase valuable mineral recovery. Based on this, the effects of nanobubbles (NBs) and hydrodynamic parameters on coarse quartz particle flotation were systematically investigated. Mechanical flotation experiments were carried out using the 7 cm and 9 cm diameter impellers in order to produce different hydrodynamic conditions. 900–1300 rpm impeller speeds were used for the 7 cm diameter impeller and 554–786 rpm for the 9 cm diameter impeller. The results show that the presence of NBs increased the flotation recovery of −425 + 106 μm quartz by up to 21%. For the 7 cm diameter impeller, the maximum flotation recoveries of 86.4% and 98% were obtained in the absence and presence of NBs at Reynolds number (Re) of 81,000 and 66,000, respectively. For the 9 cm diameter impeller, the maximum recoveries of 86.3% and 97.5% were obtained in the absence and presence of NBs at Re of 90,000 and 75,000, respectively. NBs increased the flotation rate constant up to 36%. Keywords: Flotation, Nanobubbles, Coarse particle, Quartz, Hydrodynamic parameters

The flow pattern in centrifugal pump is critical for better understanding the effect of inlet gas on the pump performance. In this study, the bubble dynamic behavior and its influence on the flow pattern in the impeller were investigated. The effects of inlet gas volume fraction, the liquid flow rate and the rotational speed on the flow pattern were analyzed. Then the effect of flow pattern on the pump performance were discussed. The results show that there are four typical flow patterns, i.e., the Bubble Flow, the Agglomerated Bubble Flow, the Gas Pocket Flow and the Segregated Flow, in the impeller. The bubble dynamic behaviors, such as the deformation, breakup and coalescence are closely related with formation of flow pattern in impeller. The flow pattern changed from Bubble Flow pattern to Segregated Flow pattern gradually as the inlet gas volume fraction increased. The gas carrying capability of pump was improved with the liquid flow rate and the rotational speed increasing. The pump performance rapidly deteriorated when the flow pattern in the impeller changed from the Gas Pocket Flow to the Segregated Flow. The liquid flow rate also affected the pump pressure increment and efficiency by changing the flow pattern in the impeller. Furthermore, the pressure increment and the efficiency of the pump increased as the rotational speed increased.

[EN]There is a need in manufacturing as in machining of being more productive. However, at the same time, workshops are also urged for lesser energy waste in cutting operations. Specially, rough milling of impellers and bladed integrated disks of aircraft engines need an efficient use of energy due to the long cycle times. Indeed, to avoid dramatic tool failures and idle times, cutting conditions and operations tend to be very conservative. This is a multivariable problem, where process engineers need to handle several aspects such as milling operation type, toolpath strategies, cutting conditions, or clamping systems. There is no criterion embracing productivity and power consumption. In this sense, this work proposes a methodology that meets productivity and sustainability by using a specific cutting energy or sustainable productivity gain (SPG) factor. Three rough milling operations-slot, plunge nad trochoidal milling-were modelled and verified. A bottom-up approach based on data from developed mechanistic force models evaluated and compared different alternatives for making a slot, which is a common operation in that king of workpieces. Experimental data confirmed that serrated end milling with the highest SPG value of 1 is the best milling operation in terms of power consumption and mass removal rate (MRR). In the case of plunge milling technique achieve an SPG < 0.51 while trochoidal milling produces a very low SPG value. The authors acknowledge the support from the Spanish Government (JANO, CIEN Project, 2019.0760) and Basque Government (ELKARTEK19/46, KK-2019/00004). This research was funded by Tecnologico de Monterrey through the Research Group of Nanotechnology for Devices Design, and by the Consejo Nacional de Ciencia y Tecnologia de Mexico (Conacyt), Project Number 296176, and National Lab in Additive Manufacturing, 3D Digitizing and Computed Tomography (MADiT) LN299129. The authors also acknowledge the support from Garikoitz Goikoetxea and fruitful discussions with Mr. Jon Mendez (Guhring (c)) and Endika Monge (Hoffmann Group (c)).

Additive manufacturing (AM) has enabled the creation of geometrically complex parts for a range of industries. However, the nature of AM often requires multiple post processing techniques to be carried out to reach the desired material properties or required surface finish. This often involves heat treatment (HT), shot peening (SP) or laser shock peening (LSP). To date, hardly any process chain modelling has been carried out on manufacturing applications with AM. This investigation focuses on the finite element (FE) modelling of the complete manufacturing process chain of an AM impeller made of IN718, including the AM, HT, LSP and SP processes. The particular AM process applied to build the impeller is laser powder bed fusion (L-PBF). Each FE process is validated individually against experimental data before being applied to the impeller process chain. The validated data from each process is mapped to the next process in the chain to investigate the combined effects of manufacturing and post processing techniques. Results have shown that high tensile residual stresses induced by AM can be reduced by approximately 75% by applying HT. SP and LSP processes can further modify remaining tensile residual stresses after HT by inducing a layer of compressive stresses at the surface. In summary, this research work has demonstrated that the simulation of AM process chains using finite element techniques is sufficiently mature to support the product and process development of industrial AM components.

Centrifugal pumps constitute one of the most common and fundamental components in many industrial processes and other technical works and applications, and their reliable and efficient operation is vital. An important hydrodynamic excitation mechanism that can affect the smooth and efficient operation of a centrifugal pump is cavitation, which may be created in the low static pressure zone of the impeller. The reliquification of the vapor bubbles at downstream positions is a violent implosion procedure that generates shock pressure waves of extreme local intensity (cavitation noise). When the vapor bubbles implode close to the solid surfaces of the pump, they cause extended wear and material removal. The amount of damage depends on the intensity and extent of the phenomenon and on the duration of operation of the pump under two-phase flow conditions. Eventually, the wear due to cavitation development in a pump is accompanied by strong vibrations and a drop in performance. Chapter 5 presents the conditions and various types of vapor formations that may appear in centrifugal pumps and summarizes the state-of-the-art experimental and numerical works that deal with the study and the diagnosis of this complex dynamic phenomenon.

An approach for the numerical topology optimization of baffled stirred tanks is presented and demonstrated exemplarily on impeller blades. The methodology is based on the well-known Brinkman penalization method, which is used to alter the impeller blade geometry without having to adapt the computational grid. Since the simulation of this time-dependent problem is computationally very expensive, non-uniform rational basis splines are employed to describe the interface between solid and fluid. This method allows topological changes of complex geometries to be realized with a minimum number of design variables, thus speeding up the optimization process. Two test cases are investigated to demonstrate the capabilities of the approach and serve as a proof-of-concept. In the first case, the power requirement of the stirrer is minimized, while the second case aims to maximize the degree of mixing. As the result of the second test case is at first useless from a practical point of view, an additional constraint is introduced to limit the maximum allowable displacement of the impeller blade, which is computed using a finite element analysis.

Flow behaviour of powders plays an important role in defining their performance in many industries. In this study, we present our work on prediction of flow characteristics of binary and ternary mixtures under dynamic conditions using Discrete Element Method and simulating the expended mechanical work of a rotating impeller penetrating a packed bed. Three commonly used methods for calculating a mean have been explored to express the mixture Bond number, namely arithmetic, geometric and harmonic mean. This is done by introducing a weighting factor based on the fractional surface area of each component of the mixture. The mixture Bond number is dependent on the interfacial surface energy, particle size and density; and a wide range of Bond number is covered in our study by varying all three. The expended work of impeller shows the clearest trend with the mixture Bond number when it is expressed in terms of the arithmetic mean. Although we only used binary and ternary mixtures (40 different mixtures in total) in this study, the trend should be applicable to multi-component mixtures and therefore useful as a design aide for powder formulation.

Bubble size is an important variable in aerated stirred tanks as it determines the surface area available for reactions. In the bubble break-up process, impellers play a key role. Despite this importance, research into the effect of impeller design on bubble size is scarce. In this work we study the effect of two impellers, with and without a stator, as well as the effect of airflow rate, impeller speed and surfactant concentration on bubble size. Results show that there is a critical impeller speed above which bubble size is not further decreased, regardless of the airflow. Operating at this critical speed results in the smallest bubble size possible without additional turbulence. The reduction in bubble size caused by a stator was quantified for the first time and, interestingly, it was found that the stator also reduced the critical coalescence concentration. The implications of these findings for the design, evaluation and optimisation of impellers are discussed.

[EN] Developments in computing infrastructure and methods over the last decade have enhanced the potential of numerical methods to reasonably predict the aerodynamic noise. The generation and propagation of the flow induced noise are aerodynamic phenomena. Although the fluid flow dynamics and the resultant acoustics are both governed by mass and momentum conservation equations, former is of convective and for diffusive nature while the latter is propagative showing insignificant attenuation due to viscosity except for small viscothermal losses. Aeroacoustic modelling of systems with intricate geometries and complex flow is still not mature due to challenges in the accurate tractable representation of turbulent viscous flows. Therefore, state-of-the-art for computing flow-induced noise in small centrifugal compressors is reviewed and critical evaluation of various parameters in the numerical model is undertaken in this work. The impact of various turbulence formulations along with corresponding spatial and temporal resolutions on performance and acoustic predictions are quantified. The performance predictions are observed to be within 1.5% of the measured values irrespective of turbulence and timestep parameters. The noise generated by the impeller is observed to be reasonably correlated with the measurements and the absolute values of the sound pressure levels along with decay rates predicted by LES and SBES formulations are better than the similar predictions from DES and URANS formulations. The impact of timestep size is observed and is determinant of the frequency up to which spectra can be appropriately resolved. Furthermore, results emphasise the importance of high spatial resolution for scale resolving turbulence formulations to yield better results and the information can be used to select appropriate numerical configuration considering time and accuracy trade-offs. (C) 2020 Elsevier Masson SAS. All rights reserved., The project is sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C). The authors would like to thank BorgWarner Turbo Systems for permission to publish the results presented in this paper. The support of the HPC group at the University of Huddersfield is gratefully acknowledged.

Agitated photobioreactors (PBR) have been widespread for the cultivation of microalgae because of their advantages in mixing and mass transfer conditions. However, it is difficult to investigate the behaviors of cultivation broth flow with experimental procedures in these PBRs. Computational Fluid Dynamics (CFD) is a common method that has been used to simulate the performance of fluid containing systems in order to investigate the fluid flow, reduce the design cost and improve the efficiency. the objective of this study was to evaluate hydrodynamics and mixing conditions of stirred tank PBR for Haematococcus pluvialis production experimentally and numerically. the cells were first cultivated in a stirred tank PBR containing Rushton turbine impeller and the cell growth was examined during 10 days. At the end of cultivation, the cell concentration was reached the value of 3.1 +/- 0.1 x 10(5) cells mL(-1) with the total carotenoid content of 2.47 +/- 0.01 mg L-1. Then, the hydrodynamic analyses were conducted to evaluate the average velocity magnitude, turbulence properties and dead zone inside the PBR. the simulation results obtained from realizable k-epsilon turbulence model showed that the uniformity index of average velocity was found as 0.86. This result showed that the fluid flow showed similar behavior in the most parts of PBR except around the impellers. the velocity contours supported that the mixing conditions were supplied efficiently, however the vortex formation was observed around the impellers in spite of the baffles. in addition, the turbulence kinetic energy having a vital influence on mixing characteristics was found between the values of 1.0 x 10(-2) and 3.0 x 10(-2) m(2) s(-2) and the lowest values were observed between two impellers due to extent of mixing. Obtained results could be used to re-design PBR configurations considering the impeller type, the distance between impellers and cultivation conditions., Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [115M014], This study was a part of Cost action ES1408 and the authors would like to thank the Scientific and Technological Research Council of Turkey (TUBITAK) with the project number of 115M014 for the financial support.

Graphical Abstract Unlabelled image, High shear wet granulation (HSWG) is one of the most poorly understood processes with known difficulties in optimization and scale up. The purpose of the current study is to develop a DEM model which can be applied under dynamic process conditions with high predictive capacity to improve process insight. The DEM model is used to predict agglomeration as a function of impeller speed and liquid addition rate in a high shear wet granulator. The DEM model tracks dynamic formation and breakage of liquid bridges between particles as liquid binder in the system is added, and corrects for the change in material properties as a function of the binder content.

This paper presents the design of a centrifugal compressor for high-speed turbomachinery. The main focus of the research is to develop a centrifugal compressor with improved aerodynamic performance. As a meridional frame has a significant effect on overall performance of the compressor, special attention has been paid to the end wall contours. The shroud profile is design with bezier curve and hub profile with circular arc contour. The blade angle distribution has been arranged in a manner that it merges with single value at impeller exit. The rake angle is positive at leading edge and negative at trailing edge with identical magnitude. Furthermore, three-dimensional straight line element approach has been used for this design for better manufacturability. The verification of the aerodynamic performance has been carried out using CFD software with consideration of a single blade passage and vaneless diffuser. The result has been compared with matching size aftermarket compressor stage gas stand data. The compressor stage with Trim 55 provides 34% increase in choke flow at 210000 RPM as compared to gas stand data with 87% peak stage efficiency at 110000 RPM. In addition, new surge margin improvement technique has been proposed by means of diffuser enhancement. This technique provides an average of 16% improvement in surge margin compared to standard diffuser stage with 55 trim compressor impeller. The mechanical integrity has been validated at maximum RPM with the aluminum alloy 2014-T6 as a fabrication material. Keywords: Centrifugal compressor, Aerodynamic performance, Surge margin, Blade angles, Stress analysis, Computational fluid dynamics

In this paper, the data assembled concerning the agitation of a Newtonian fluid in a cylindrical vessel is disclosed. The stirred vessel is not provided with baffles and has a flat-bottom. The data presents some information on the characteristics of two impellers: a six-blade Rushton turbine and a six-blade paddle impeller. The flow patterns generated by both impellers are depicted and compared. Also, the power required when changing the impeller rotational speed is given. The data summarized here via three-dimensional calculations of velocities and viscous dissipation in the whole volume of the tank provides additional knowledge for the best choice of impellers for each industrial process. Keywords: Stirred tank, Rushton turbine, Paddle impeller, Power input, Flow patterns

Present work compares the mass transfer coefficient (kLa) and power draw capability of stirred tank employed with Rushton and curved blade impeller using computational fluid dynamics (CFD) techniques in single and double impeller cases. Comparative analysis for different boundary conditions and mass transfer model has been done to assess their suitability. The predicted local kLa has been found higher in curved blade impeller than the Rushton impeller, whereas stirred tank with double impeller does not show variation due to low superficial gas velocity. The global kLa predicted has been found higher in curved blade impeller than the Rushton impeller in double and single cases. Curved blade impeller also exhibits higher power draw capability than the Rushton impeller. Overall, stirred tank with curved blade impeller gives higher efficiency in both single and double cases than the Rushton turbine

The aerated power consumption characteristics in a transparent tank with diameter of 0.3 m and flat bottom stirred by a Rushton impeller were investigated by means of experimental measurement. The test fluid used was tap water as liquid and air as gas. Based on Weibull model, the complete correlation of aerated power with aerated flow number was established through non-linear fit analysis. The effects of aerated rate and impeller speed on aerated power consumption were made an exploration. Results show that the changeable trend of the aerated power consumption is found to be similar under different impeller speeds and impeller diameters, i.e. the aerated power is close to dropping linear at the beginning of gas input, and then the drop tendency decreases as the aerated rate increases, at the end, the aerated power is a constant on the whole as the aerated rate reaches up the loading state. The non-linear fit curve is done using the software Origin based on the experimental data. The fairly high precision of data fit is obtained, which indicates that the mathematical model established can be used to accurately predict the aerated power consumption, comparatively. The proposed research provides a valuable instruction and reference for the design and enlargement of stirred vessel. Keywords: Gas-liquid stirred tank, Aerated power consumption, Aerated flow number, Mathematical model

The fundamental way of improving the mixing efficiency is to induce the chaotic flow in a stirred vessel. The impeller form plays an important role for changing the structure of flow field and realizing chaotic mixing. Based on the velocity time series acquired by the experiment of particle image velocimetry (PIV), with the software Matlab, the macro-instability (MI), largest Lyapunov exponent (LLE), and Kolmogorov entropy in the water stirred tank is investigated respectively with the impeller of perturbed six-bent-bladed turbine (6PBT). The results show that the MI characteristics are obvious and two peak values of MI frequency are observed at the speed N = 60 rpm. With the increasing speed (more than 100 rpm), the peak characteristics of MI frequency disappear and a multi-scale wavelet structure of characterizing the chaotic flow field appears. Moreover, under the speed N = 60 rpm, the LLE is less than 0 and Kolmogorov entropy is 0, which means that the flow field is in the periodic moving state. As the speed is increased to more than 100 rpm, the LLE and Kolmogorov entropy are all more than 0, which indicates that the flow field goes into the chaotic mixing. When the speed reaches up to about 210 rpm, both of the LLE and Kolmogorov entropy achieve the optimum values, which will result in an excellent chaos with the highest mixing efficient. So it is feasible that the MI frequency, the LLE and the Kolmogorov entropy can be used to analyze the flow field characteristics in a stirred tank. The research results promote the understanding of the chaotic mixing mechanism and provide a theoretical reference for the development of new type impeller. Keywords: Macro-instability, The largest Lyapunov exponent, Kolmogorov entropy, The impeller of perturbed six-bent-bladed turbine, Chaotic mixing, PIV

Dye visualisation techniques and CFD are used to characterise the flow of viscoplastic Carbopol™ solutions in stirred vessel systems over multiple scales. Centrally-mounted, geometrically-similar Rushton turbine (RT) impellers are used to agitate various Carbopol 980 (C980) fluids. The dimensionless cavern diameters, Dc/D, are scaled against a combination of dimensionless parameters: Rem−0.3Rey0.6n−0.1ks−1, where Rem, Rey, n and ks are the modified power-law Reynolds number, yield stress Reynolds number, flow behaviour index and impeller geometry constant, respectively. Excellent collapse of the data is demonstrated for the fluids and range of flows investigated. Additional data are collected using a pitched-blade turbine (PBT) with cavern size similarity being shown between the RT and PBT datasets. These results are important in the context of scale-up/scale-down mixing processes in stirred vessels containing complex fluids and can be used to show that flow similarity can be achieved in these systems if the processes are scaled appropriately.

The hydrodynamic behavior of a turbulent flow and the mixing characteristics generated by a V-grooved axial impeller inside an agitated tank reactor were investigated both experimentally and numerically. Angle resolved Particle Image Velocimetry (PIV) techniques with an angular displacement Δθ = 5° have been applied and two aerodynamic planes along the blades were considered. PIV-based results were compared to those obtained by Large Eddy Simulation (LES), used with the dynamic Smagorinsky-Lilly sub-grid scale (SGS) model. Results showed the existence of distinctive recirculation zones in the aerodynamic planes, and new additional frequencies in the impeller stream, induced by the grooves. A decrease of mixing time of about 11% was obtained experimentally, consequence of the better suction induced by the grooved blades in the early stages of mixing. Mean velocities, vorticity, TKE obtained from LES showed a good agreement with the PIV-based results. The distributions of turbulence dissipation rate e were similar to those obtained from PIV, however showing high under-predicted magnitudes.

[EN] The operation of compressor at lower mass flow rates is limited by surge which is marked by large fluctuations in operational variables and accompanied by significant increase in noise. Ported shroud casing treatment is a widely used method to control the flow near unstable conditions in order to obtain a stable operation and enhance deep surge margin. The research on the acoustic effects of the ported shroud design is limited. Therefore, this paper numerically characterises the acoustic features of a turbocharger compressor with ported shroud design operating at marginal or soft surge conditions and investigates the correlation between acoustic characteristics and the spatial flow structures. The acoustic and the flow field features are analysed using spectral signatures obtained from an experimentally validated numerical model using both performance and acoustic measurements. Propagation of the frequency content through the ducts has been estimated with the aid of the beamforming and method of characteristics to enhance the content coming from the compressor. Expected acoustic phenomena such as rotating order tones and blade passing peaks are correctly identified in the modelled spectrum with the limitation to capture the specific broadband features. Hence, the numerical model can be used to further the research encompassing the impact these flow enhancement solutions have on the noise emission of the turbocharger. Inspection of the flow field shows radially exiting fluid at the ported shroud slot leading to the formation of the high-speed jets exiting the ported shroud cavity. Circumferential propagation of the stall cells is also identified in the impeller. Further inspection of the pressure field through modal decomposition implies the localisation of the energetic noise sources in the impeller downstream components. The influence of the ported shroud cavity on the acoustic characteristic of the compressor is not significant and is limited to the propagation of the tonal noise in the direction of impeller upstream. (C) 2019 Elsevier Ltd. All rights reserved., The project is sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C). The authors would like to thank BorgWarner Turbo Systems for permission to publish the results presented in this paper. The support of the HPC group at the University of Huddersfield is gratefully acknowledged.

In this work, a model of a 218 L scale pharmaceutical antisolvent crystallization process was developed. The model is based on a hybrid method of computational fluid dynamics (CFD) and compartmental modeling. In the model, the mixing behaviour of the bulk fluid at two different impeller speeds was obtained from CFD simulations. The compartmental map of the crystallizer was extracted from CFD results based on a hypothesis driven compartmentalization approach. A novel dynamic compartment model was developed to capture the fluid dynamics during the feeding of the antisolvent into the crystallizer and implemented in MATLAB/Simulink environment. Developed model takes into account the changes in compartmental volume, solvent concentrations and density and it assumes a dynamic flow between compartments during the filling. Dynamic compartment model can be also applied in other areas of modeling practices in chemical engineering instead of steady-state compartment models such as fed batch fermentation.

In this chapter, we deal with turbomachinery rotor repairs because a reliability-focused user will seek involvement in all critical phases of the compressor repair process. Compressor rotor repairs as they pertain to the two styles of rotors, the built-up and the drum type version, are being examined by discussing manufacturing techniques and overspeed testing of impellers, their material of construction, attachment methods to the shaft, design problems, balancing procedures, and special difficulties. The chapter then proceeds to describe the nature of rotor bows in compressors and steam turbines and how to recover from these events. One particular activity around rotors is balancing which is thoroughly described in Chapter 6 . Clean up and inspection of rotor is of utmost importance, and the authors devote therefore a great deal of space and time to this subject. This includes remarks on disassembly of rotor for shaft repair including shaft design, material of construction and inspection. The following issues are discussed: Rotor assembly, the effects of thrust forces on bearings, thrust balance compensation and retrofit design solutions. The authors decided to deal with managing rotor repairs at outside shops highlighting the importance of the following steps: Inspection, Disassembly, Stacking, and Balance of Centrifugal Compressor Rotors, as well as incoming inspection procedures, assembly, interfacing with shop personnel and sub-vendors. Finally, a sizable portion of the chapter is dedicated to mounting of hydraulically fitted coupling hubs. Here the reader will become familiar with the various steps leading to the successful mounting and dismounting of hydraulically fitted couplings.

This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) The paper focuses on understanding the performance of a vaned diffuser in a supercritical CO 2 compressor using real gas assumptions. The rapidly changing properties of CO 2 in the non-ideal thermodynamic region can have a significant impact on the performance of the diffuser. To account for this, the relationship between the flow properties (i.e. fundamental derivative) and the local geometry (i.e. cross-sectional area of the nozzle) has been discussed theoretically. To examine it analytically, the study has considered the influence of real gas properties on the performance of a vaned diffuser using computational fluid dynamics (CFD) modelling. The selected compressor stage geometry is similar to the compressor impeller tested in the Sandia sCO 2 compression loop facility. The effect of changes in the number of blades and the corresponding changes in the cross throat area on the flow properties such as density and speed of sound were investigated and discussed. The results illustrate that a diffuser with a higher number of blades (smaller throat area) compared to a diffuser with a wider throat area has a higher probability of creating flow instability in the passage stage. European Union’s Horizon 2020 research and innovation programme and Research Councils UK

The force exerted by wet mass in a granulator on a thin cylindrical probe called the drag force flow (DFF) sensor reflects wet mass consistency and is indicative of the granule densification. Comparison of flow force during wet granulation of batches with different binder concentration indicated good correlation with the granulation's resistance to flow and interparticulate interactions measured by the FT4 Powder Rheometer. This indicated that the force pulse magnitude (FPM) measured by the DFF sensor was indicative of fundamental material properties (e.g., shear viscosity and granule size/density). In addition, the time-profile of the FPM signal from the DFF sensor compared well with that of the impeller amperage, with consistent differentiation between different formulations.

The paper focuses on the data collected from the mixing of shear thinning non-Newtonian fluids in a cylindrical tank by a Rushton turbine. The data presented are obtained by using Computational Fluid Dynamics (CFD) simulation of fluid flow field in the entire tank volume. The CFD validation data for this study is reported in the research article ‘Numerical investigation of hydrodynamic behavior of shear thinning fluids in stirred tank’ (Khapre and Munshi, 2015) [1]. The tracer injection method is used for the prediction of mixing time and mixing efficiency of a Rushton turbine impeller. Keywords: Non-Newtonian fluids, Rushton turbine, Mixing time, Mixing efficiency, Cylindrical tank

Two austenitic stainless steel grades, 316L and 904L, and three duplex stainless steel grades, LDX 2101, 2205, and 2507, were erosion–corrosion tested as impeller blade materials for hydrometallurgical applications. Samples were attached to the pressure and suction sides of an impeller and were tested in 50 g/l H 2 SO 4 and 0.5 g/l Fe 2 (SO 4 ) 3 for 72 h at 80°C and 95 °C in a small-scale reactor using quartz sand slurry. The results showed that under lower erosion intensity the ranking of the grades was similar to that in pure erosion. Under higher erosion intensity the ranking of the grades changed completely: lean alloys LDX 2101 and 316L suffered from the highest mass losses followed by 2205, 2507, and 904L. To clarify this behavior, the ability of the grades to repassivate was investigated with scratch tests. It was found that the ranking could be explained by the repassivation rates. The only exception was that 2507 showed a similar repassivation rate to 904L but its erosion–corrosion mass loss under higher erosion intensity was larger. One contributing factor to this was found to be the selective dissolution of the austenite phase of all the tested duplex grades. The prerequisites for the galvanic coupling between the phases that was responsible for the selective dissolution are discussed.

[EN] State of the art techniques for reducing pollutant emission in internal combustion engines often require local flow assessment, specially in the air management field. This work addresses the interaction between a turbo- charger compressor and the 3-way long-route EGR joint, where exhaust gases of the combustion are mixed with fresh air. A validated methodology for compressor simulation is combined with a validated condensation model for this work. Numerical simulations of two different working points with three flap positions are conducted. The influence of these operating conditions on the flow field is evaluated. Particularly, there is a connection between the mixing of both steams and the generation of water condensates, responsible for the erosion of the impeller and the loss of compressor efficiency. Moreover, neglecting the impact of the compressor presence on the condensation production is shown to be of low magnitude, so that simulations without the compressor are regarded as accurate, thus reducing the computational effort by two orders of magnitude., Daniel Taxi is partially supported through contract FPI-S2-2015-1095 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.

The effect of applied shear stress on Botryococcus braunii, in the presence of solvent is important to further understanding the mechanisms behind in-situ solvent extraction and will be critical in the design and scale up of an effective extraction process. This paper looks at the effect of various mixing rates on colony structure and culture photosynthetic activity in the presence of heptane. Partial colony disruption was found to occur at shear rates of 335 s− 1, with the main mechanism of disruption believed to be microeddies generated by turbulence around the impeller. Photosynthetic activity was seen to drop by 55 % during the extraction period requiring a short recovery time of 3 days, reaching 66.5 % of its original value. These results provide valuable insight and data on the shear limits of B. braunii required in the design of a repeated milking process and will assist in the design and scale up of a viable milking process.

Herein, a new passive control system for limiting cavitation inside turbomachinery has been applied to a NACA0009 hydrofoil. The basic idea is to introduce slots nearby its leading edge, connecting pressure and suction sides of the hydrofoil, in order to increase locally the pressure on its suction side and to prevent cavitation from developing. The cavitating flow developed around a two-dimensional hydrofoil is here considered since it is an archetype of cavitation nearby the leading edges of the impeller vanes. Thus, the flow field developed at the leading edge of both the original and modified hydrofoil has been studied at different angles of attack in order to reproduce a wide range of operating conditions that occur inside turbomachinery. Eventually, a comparison of their performance in terms of polars (CL and CD) and vapour volume fractions (αv) is performed.

Second-generation ventricular assist devices (VADs) emerged after the first-generation, which had proven that mechanical assistance of the ventricular function is a promising therapy. However, the technological limitations of first-generation devices increased the need for more reliable mechanical circulatory support. This inspired clinicians, scientists, and engineers to evaluate the rotary pump principle. These so-called second-generation VADs were used as extracorporeal, paracorporeal, less invasive, or long-term support devices. In this textbook, all rotary pump devices without a full levitation system of the impeller are categorized as second-generation VADs. Starting with the HemoPump in the late 1980s, several developments were triggered, resulting in an innovative decade of the 2000s with the emergence of a plurality of implantable VADs. Soon, improved outcomes became apparent, and, with the publication of randomized clinical studies, the superiority of the rotary pump principle was proven for left ventricular assistance. It was thus established that these so-called continuous-flow devices, which almost completely attenuate the residual pulse, are a feasible and effective long-term therapy. The future for second-generation pump technology might be for special applications such as for the pediatric patient population, for the right ventricle, or partial support.

International audience; Continuous powder processes, such as continuous powder mixing, are more than ever envisioned as a viable alternative to batch equipment, in various industries such as pharmaceuticals, specialty chemicals (zeolites, SiC), bio-renewables or food. In the present work we have implemented an on-line image analysis set-up that is able to capture all the images of the partides at the outlet of a continuous pilot-scale mixer. This allows the determination of the homogeneity of mixtures of two different compositions, as well as the analysis of their evolution during steady-state and transitory regimes. The importance of a proper definition of the scale of scrutiny of the mixture is emphasized by providing homogeneity results obtained at four different scales. Evidence of segregation by percolation giving rise to the enrichment of the mixer's bed with fine particles is given and commented. The impact of the stirrer's rotational speed on the quality of the mixtures, as provided by the coefficient of variation CV, is reported. Up to 20 Hz, CV's are extremely high, while above 30 Hz, the influence of the impeller speed is much weaker. Finally, the influence of impeller speed's step perturbations is measured and commented. Due to the size- segregation phenomenon inside the mixer, negative steps are deeply detrimental to the mixing process. On the contrary, positive steps can be absorbed by the equipment without degradation of the quality of the mixtures.

Multi-phase materials are common in several fields of engineering and rheological measurements are intensively adopted for their development and quality control. Unfortunately, due to the complexity of these materials, accurate measurements can be challenging. This is the case of bitumen-rubber blends used in civil engineering as binders for several applications such as asphalt concrete for road pavements but recently also for roofing membranes. These materials can be considered as heterogeneous blends of fluid and particles with different densities. Due to this nature the two components tends to separate and this phenomenon can be enhanced with inappropriate design and mixing. This is the reason behind the need of efficient dispersion and distribution during their manufacturing and it also explains while real-time viscosity measurements could provide misleading results. To overcome this problem, in a previous research effort, a Dual Helical Impeller (DHI) for a Brookfield viscometer was specifically designed, calibrated and manufactured. The DHI showed to provide a more stable trend of measurements and these were identified as being “more realistic” when compared with those obtained with standard concentric cylinder testing geometries, over a wide range of viscosities. However, a fundamental understanding of the reasons behind this improvement is lacking and this paper aims at filling these gaps. Hence, in this study a tailored experimental programme resembling the bitumen-rubber system together with a bespoke Computational Fluid Dynamics (CFD) model are used to provide insights into DHI applicability to perform viscosity measurements with multiphase fluids as well as to validate its empirical calibration procedure. A qualitative comparison between the laboratory results and CFD simulations proved encouraging and this was enhanced with quantitative estimations of the mixing efficiency of both systems. The results proved that CFD model is capable of simulating these systems and the obtained simulations gave insights into the flow fields created by the DHI. It is now clear that DHI uses its inner screw to create a vertical dragging of particles within a fluid of lower density, while the outer screw transports the suspended particles down. This induced flow helps keeping the test sample less heterogeneous and this in turns allows recording more stable viscosity measurements. This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) [grant number EP/M506588/1 ].

One of the main features of animal cell bioreactors is that the cultured cells lack a strong membrane and are therefore more prone to shear damage. It is widely accepted that animal cell damage in aerated bioreactors is mainly related to burst bubbles at the air–liquid interface. A viable alternative to sparged bioreactors, aimed at minimizing cell damage, may be represented by uncovered, unbaffled, stirred tanks, which are able to provide sufficient mass transfer through the deep free surface vortex that takes place under agitation. As a consequence the need for bubble formation and subsequent bursting accompanied by cell damage is conveniently avoided. In this chapter, mass transfer performance and hydrodynamic features (e.g., free surface shape, mixing time, power consumption) of this kind of bioreactor are described. The effects of changing liquid viscosity, impeller geometry, and reactor aspect ratio are also discussed.

Hundreds of books and many thousands of articles describe, explain, and expound on dynamic compressors. They are categorized as dynamic compressors because their operating principle is to impart velocity to a gas entering into impellers or blades. The gas exits the blades and reenters into a stationary volume where the velocity energy is transformed into pressure energy. Centrifugal and axial compressors are found in many industries where they feed, transport, or compress gases in a host of different processes. To some extent, the two duty points, pressure and flow of dynamic compressors, overlap with those of certain positive displacement compressors. We are placing several related topics in this subject category.