Impeller Rotational Speed Research Articles

Use of Gas Helicity as an Indicator to Evaluate Impeller Design and its Gas Holdup: Proof of Concept for the Intensification of Gas-Liquid Mixing

The fundamental insights into the impact of impeller geometry on the gas helicity can help equipment suppliers to design more energy-efficient impellers while reducing the overall energy expenses of wastewater plants and aerobic fermenter. In this perspective, the proof of concept was developed using electrical resistance tomography and computational fluid dynamics (CFD) modelling. At a fixed speed ratio (central impeller rotational speed/ anchor rotational speed), the sign of gas helicity (+ or -) provides insights about the gas velocity direction and the degree of gas holdup in non-Newtonian fluid. The predicted gas holdup was within the range of experimental measurement. In this experiment, the carboxymethyl cellulose (1 wt% CMC) solution was used. It is a non-Newtonian fluid which obeys the power law model. The ASI impeller was the most energy-efficient impeller which generate reasonable aeration efficiency with negative helicity. The poor aeration efficiency of some novel impellers such as ASI Slanted and PBT Up-Down were attributed to the fluctuations in the gas helicity sign. The proof of concept shows that the local helicity analysis can be insightful to better understand gas-liquid mixing and further intensify gas dispersion. The lift force generated by these impellers can be useful for anaerobic digester.

Transition from binder to matrix-forming: The effect of hydroxypropylmethylcellulose concentration on the properties of starch/hydroxypropylmethylcellulose granules prepared in a high shear granulator

The effects of the hydroxypropylmethylcellulose (HPMC) concentration and the operation parameters on the starch/HPMC granule properties prepared in a high shear granulator are investigated. At a lower concentration of 3.8% or 4.9%, HPMC acts as an intergranule binder. At a higher concentration of 7.2%, HPMC acts as an intragranule matrix-forming polymer. At the intermediate HPMC concentration of 6.1%, HPMC shows dual roles as a binder and as matrices. At the intermediate HPMC concentration, a new granule oscillating growth profile is observed. The impeller rotational speed has a more pronounced effect on the granule size distribution at the intermediate HPMC concentrations. The prepared granules are rounder and have narrow size distributions. The granules also show the highest compaction loading of 140 N and the highest tablet crushing force of 39.95 N.

Effect parameters of vertically spindle cotton picker machines on the mechanical damage of cotton seeds during machine harvesting

The article describes the influence of factors as a suction and injection method of transporting raw cotton from a harvesting machine to the mechanical damage of cotton seeds. The influence of the rotation speed and design of the fan impeller, as well as the width of the working slit of the harvesting apparatus on the formation of an undesirable defect, that is, mechanical damage to cotton seeds are examined. Recommendations are proposed to reduce the mechanical damage to cotton seeds.Rotating the spindle together with the drum, the cotton is transported to the pick-up area, where due to the spindle reversal due to the epicycle mechanism of its drive, the bulk of the cotton is inertia (up to 75-80%) discharged from the spindle surface, and part of the cotton windings is removed by brush pullers rotating in the same direction ( while the linear speed of the brushes is 4 times greater than the peripheral speed of the spindle) and under the action of centrifugal force, the cotton from the surface of the puller is dumped into the slotted receiving chamber of the harvester apparatus.

CFD investigation of the agitation in the desupersaturation during the wet-process phosphoric acid (WPPA) process

Abstract Desupersaturation is a complex cooling operation that involves hydrodynamic, thermal and mechanical phenomena. This process requires continuous agitation to avoid fouling problems and sludge deposition. The current work aims to investigate the well mixedness in the desupersaturation tank for optimal performance. For this purpose, a multi-fluid CFD study was conducted based on the Euler–Euler modeling approach, considering a multi-phase flow involving a liquid phase (phosphoric acid) and a poly-dispersed solid phase, i.e. a sludge with three different sizes where each size is considered as a separate phase. First, the hydrodynamic behavior of the flow within the agitated desupersaturator is analyzed through the investigation of the velocity fields as well as the power and pumping numbers, to determine both the agitator capacity to pump the flow and its power consumption during the operation. Then, in order to assess the mixture homogeneity, we evaluated the solid suspension in the desupersaturation reactor following conventional methods and two new proposed methodologies: the first approach is to evaluate the suspension quality in the mixing system by compartment and the second consists on the assessment of the uniform convergence of the solid concentration. Furthermore, we calculated the time required to achieve a full suspension at different solid concentrations. On other hand, we conducted a detailed analysis of the solid distribution dependency on the impeller rotational speed at different solid volume fraction, which allows a good understanding of the parameters controlling the homogenization in the desupersaturator.

Volumetric Flow Observer For A Pumping Unit Without Backpressure With Induction Electric Drive

The article describes the construction of a volumetric fluid supply observer in pumping systems. The electric drive of the pump unit uses an induction motor with a squirrel-cage rotor. The rotation speed of the electric motor is adjustable. A centrifugal pump is used to pressurize a pipeline. Requirements for the automation level of pumping units are growing, so the research topic is relevant. When constructing the observer, the double squirrel cage induction motor model in a fixed coordinate system is used. The impeller rotation speed and the pump resistance moment were estimated based on the Luenberger observer. The observer is used to identify the volume flow. It is based on a centrifugal pump model using approximating coefficients of a Second-Degree Polynomial function. The article provides the dynamic characteristics of the reference model and observer. As a studies result, an error in the steady state operating mode of 1% was determined.

Evaluation of Aluminum Dross Generation Rate During Mechanical Stirring of Aluminum Through Model Experiment and Numerical Simulation

The present study proposed, for the first time, an evaluation method to predict the generation rate of aluminum dross in melting or holding furnaces during mechanical stirring of molten aluminum through water model experiments and numerical simulation. In the experiments, a gas–liquid interface reaction between CO2 gas and NaOH solution was exploited as a model reaction between the aluminum melt and air moisture, and perlite particles were used to model dross layer on the free surface of liquid aluminum. The results reveal that the reaction rate is increased with the impeller rotation speed. Besides, the reaction rate depends on the impeller rotation direction, but this dependence is different for the cases of presence and absence of particles on the liquid surface. In the first case, the reaction rate at the counter-clock rotation was higher than that at the clock-wise rotation. On the other hand, in the second case, the clock-wise impeller rotation yielded a higher reaction rate compared to the counter-clock rotation case. These phenomena can be explained by the mass transfer across the gas–liquid interface at the particle-free area.

Numerical simulation of transient flow in a shaft extension tubular pump unit during runaway process caused by power failure

To explore the load impact and instantaneous flow characteristics of a tubular pump under unconventional operating conditions, the runaway condition caused by the unit power failure are investigated. Unsteady three-dimensional (3D) numerical simulation and model test were executed on whole flow system of the pump, where a 3D VOF method was specifically adopted to simulate water surfaces of the upstream and downstream reservoirs. The results of numerical simulation in terms of system performance parameters and runaway speed presented a quite good agreement with the experimental data. During the transient process, both the rotational speed and flow rate of the pump unit were found to rapidly decrease with time until maximum runaway speed (1.51n0) was reached, where however, a time lag of 0.7s between the rotational speed and flow rate has been noticed. The explored increase of pressure pulsations is generally believed to have taken source from incurred water shock waves, where the main pulsation frequencies throughout the whole flow passage were the blade passing frequency (BPF) and its harmonics. Large flow vortical structures immerged within the rear guide vanes when the flow rate decreased to zero, while the same flow vortices appeared within the front guide vanes when the impeller rotational speed gradually fell to zero. This study’s results provide a meaningful reference about pump transient operations, leading to the prevention of associated structural vibrations and possible blade cracks, for safe operations of the pumping stations.

Effect of drag reducing polymers and impeller geometry on the rate of mass and heat transfer at the wall of a cylindrical stirred tank reactor in relation to catalytic reactor design

The effect of impeller geometry on the rate of liquid-solid mass transfer at the wall of the stirred tank reactor was studied by measuring the rate of the diffusion-controlled disintegration of copper in acidified dichromate. Factors examined were rotation speed of impeller and its geometry, drag reducing polymer concentration, solution physical properties and baffles effect. The mass transfer data in the blank solution were correlated by dimensionless correlations. Radial flow impellers produced higher rates of mass transfer than axial flow impellers under the same conditions. For a given set of conditions the presence of baffles was found to increase the rate of mass transfer more than unbaffled reactors. Drag reducing polymer was found to decrease the mass transfer rate by an amount ranging from 3.5 to 38.5% depending on rotation speed of impeller, polymer concentration and impeller geometry. Implication of the present results for stirred tank biochemical reactors which use drag reducing polymer to control solution viscosity and decrease the shear stress between the moving solution and the vessel wall as to protect immobilized enzyme or cells fixed to the wall against mechanical damage were discussed. The present results would help in evaluating the financial possibility of utilizing drag reducing polymers in working biochemical stirred tank reactors.

Performance of a dual helical ribbon impeller in a two-phase (gas-liquid) stirred tank reactor

The performance of a dual helical ribbon impeller in a gassed stirred tank reactor filled with a shear-thinning polymer has been investigated experimentally in this study. Sodium carboxymethyl cellulose with different concentrations were applied to change the viscosity and rheological behaviour of working fluid. Titration reaction between HCl and NaOH then took place inside the reactor under controlled pH, evaluating the influence of a dual helical ribbon impeller on the performance of a two-phase agitated reactor. The impact of impeller rotational speed, gas flow rate, viscosity, and clearance to the bottom on power uptake and mixing time are explored. The results thus reveal that the presence of bubbles reduces both required power uptake and mixing time to reach an endpoint reaction. Contrary to expectations, this study indicates that increasing the impeller's speed beyond a certain level, not only fails to further reduction in mixing time, whilst the power uptake increases exponentially.Furthermore, for the first time, this study suggest that power number is inversely proportional to the square root of Reynolds number when systems are equipped with a dual helical ribbon impeller. The response surface method and quadratic numerical models are applied to suggest models in order to calculate the mixing time and power consumption.

Screening and interaction study of the operating parameter influence the wax formation using design of experiment

Oil and gas industry has been facing the wax deposition issue due to low temperature condition during the transportation of crude oil from offshore to onshore. The most common method to overcome this problem is by injecting polymeric wax inhibitor in the pipeline. The aim of this work is focused on the screening of the factors that affect the wax deposit inhibition using two types of wax inhibitor; which are poly(ethylene-co-vinyl acetate) (EVA) and Petronas-pour point depressant (PPD) through Design Expert software version 7.1.6. The other three factors evaluated include cold finger temperature (5 & 20°C), rotation speed of impeller (100 & 600 rpm) and the duration of experiment (2 & 6 h). Sixteen experiments were run to observe the rate of wax deposition using cold finger apparatus suggested by level of factorial analysis. The results revealed a significant model with R2 value of 0.989 indicating that 98.9% of the variable response can be explained by the model. From the analysis of variance (ANOVA), factor D, which has the addition of EVA in crude oil was found to be the main factor affecting the wax deposit inhibition followed by duration of the experiment, rotation speed, cold finger temperature and Petronas-PPD factors. Furthermore, the interaction between factor D (EVA) and factor E (Petronas –PPD) shows the greatest influence to reduce wax deposition. The best configurations to minimize the amount of wax deposit were found using standard order No 1 which is at 5°, 100 rpm and for the duration of 2 h using EVA as wax inhibitor. The amount of wax deposit measured is 0.018g. Hence, it can be concluded that factor D, and interaction between factors D and E need to be focused in controlling the parameters to minimize wax deposition.

A Comparative Study on Centrifugal Pump Designs and Two-Phase Flow Characteristic under Inlet Gas Entrainment Conditions

Capability for handling entrained gas is an important design consideration for centrifugal pumps used in petroleum, chemistry, nuclear applications. An experimental evaluation on their two phase performance is presented for two centrifugal pumps working under air-water mixture fluid conditions. The geometries of the two pumps are designed for the same flow rate and shut off head coefficient with the same impeller rotational speed. Overal pump performance and unsteady pressure pulsation information are obtained at different rotational speeds combined with various inlet air void fractions (α0) up to pump stop condition. As seen from the test results, pump 2 is able to deliver up to 10% two-phase mixtures before pump shut-off, whereas pump 1 is limited to 8%. In order to understand the physics of this flow phenomenon, a full three-dimensional unsteady Reynolds Average Navier-Stokes (3D-URANS) calculation using the Euler–Euler inhomogeneous method are carried out to study the two phase flow characteristics of the model pump after corresponding experimental verification. The internal flow characteristics inside the impeller and volute are physically described using the obtained air distribution, velocity streamline, vortex pattern and pressure pulsation results under different flow rates and inlet void fractions. Pump performances would deteriorate during pumping two-phase mixture fluid compared with single flow conditions due to the phase separating effect. Some physical explanation about performance improvements on handing maximum acceptable inlet two phase void fractions capability of centrifugal pumps are given.

Classification performance of model coal mill classifiers with swirling and non-swirling inlets

Abstract The classification performance of model coal mill classifiers with different bottom incoming flow inlets was experimentally and numerically studied. The flow field adjacent to two neighboring impeller blades was measured using the particle image velocimetry technique. The results showed that the flow field adjacent to two neighboring blades with the swirling inlet was significantly different from that with the non-swirling inlet. With the swirling inlet, there was a vortex located between two neighboring blades, while with the non-swirling inlet, the vortex was attached to the blade tip. The vorticity of the vortex with the non-swirling inlet was much lower than that with the swirling inlet. The classifier with the non-swirling inlet demonstrated a larger cut size than that with the swirling inlet when the impeller was stationary (~ 0 r⋅min-1). As the impeller rotational speed increased, the cut size of the cases with non-swirling and swirling inlets both decreased, and the one with the non-swirling inlet decreased more dramatically. The values of the cut size of the two classifiers were close to each other at a high impeller rotational speed (≥ 120 r⋅min-1). The overall separation efficiency of the classifier with the non-swirling inlet was lower than that with the swirling inlet, and monotonically increased as the impeller rotational speed increased. With the swirling inlet, the overall separation efficiency first increased with the impeller rotational speed and then decreased when the rotational speed was above 120 r⋅min-1, and the variation trend of the separation efficiency was more moderate. As the initial particle concentration increased, the cut sizes of both swirling and non-swirling inlet cases decreased first and then barely changed. At a low initial particle concentration (

Theoretical Prediction Model of Tip Leakage Vortex in a Mixed Flow Pump With Tip Clearance

Abstract Tip clearance results in the leakage flow from blade pressure side to suction side, which will further cause the tip leakage vortex (TLV). Moreover, the flow pattern in an impeller is seriously deteriorated due to the TLV and its interaction with the main stream. In this work, the TLV in a mixed flow pump is investigated by numerical simulation validated by experiment measurement. The primary tip leakage vortex (PTLV) trajectory is specially studied with consideration of the tip clearance size δ, the impeller blade number Zi, and the impeller rotational speed n. The results show that δ slightly shifts the separation point (SP) of the PTLV but rarely affects the separation angle α. The increase in Zi and the decrease in n both lead to the shift of the SP toward the blade trailing edge and the decrease in α. Furthermore, a theoretical prediction model is proposed to predict the PTLV trajectory, by which the axial position and radial position of PTLV trajectory versus the rotation angle can be predicted. The proposed model is verified to be accurate to predict the PTLV trajectory, especially for the PTLV trajectory in the main flow passage. The dynamic evolution of TLV under different tip clearance sizes can all be classified into the same three stages: splitting stage, developing stage, and merging stage. Meanwhile, the dynamic evolution frequency fe is the same as the impeller rotational frequency fi.

Experimental study on gas-liquid transient flow in liquid-ring vacuum pump and its hydraulic excitation

To study the gas-liquid flow in liquid-ring vacuum pump and its vibration characteristics, the test system was developed for flow visualization and vibration monitoring. The flow structure was captured by high-speed camera, and the vibration sensors were mounted on the bearing house and the pump casing respectively. The study shows that the vibration amplitude trends of the bearing house and pump casing are both a quadratic curve during start-up period, and the vibration amplitude of the pump casing is closely related to the unstable gas-liquid interface. With the increase of impeller rotation speed, more and more bubbles penetrate to the liquid ring, and the wakes are becoming more intense. Under different operating conditions, the main vibration of pump casing is highly relevant to the transient gas liquid flow. The main characteristic frequencies vibration of the bearing house is caused by mechanical resonance. The vibration level of the bearing house is significantly higher than the pump casing at all conditions. The vibration level of the pump casing increases with the decrease of flow rate and the increase of rotation speed for the transient flow. The vibration level of the bearing house reaches the maximum when the rotation frequency is consistent with the natural frequency.

Application of CFD to Analyze the Hydrodynamic Behaviour of a Bioreactor with a Double Impeller

Stirred bioreactors are commonly used unit operations in the pharmaceutical industry. In this study, computational fluid dynamics (CFD) was used in order to analyze the influence of the impeller configuration (Segment–Segment and Segment–Rushton impeller configurations) and the impeller rotational speed (an operational parameter) on the hydrodynamic behaviour and mixing performance of a bioreactor equipped with a double impeller. A relatively close agreement between the power values obtained from the CFD model and those measured experimentally was observed. Various parameters such as velocity profiles, stress generated by impellers due to the turbulence and velocity gradient, flow number, and mixing time were used to compare the CFD simulations. It was observed that the impeller’s RPM could change the intensity of the interaction between the impellers when a Segment–Rushton impeller was used. In general, increasing the RPM led to an increase in total power and the stress acting on the cells and to a shorter mixing time. At a constant RPM, the Segment–Rushton impeller configuration had higher total power and stress acting on cells compared to the Segment–Segment impeller configuration. At lower RPM values (i.e., 50 and 100), the Segment–Segment impeller provided a shorter mixing time. Conversely, at the highest RPM (i.e., 150) the Segment–Rushton impeller had a shorter mixing time compared to the Segment–Segment impeller; this was attributed to the high level of turbulence generated with the former impeller configuration at high RPM.

Abstract # 4263 Bate-palmas mutant mice has an increased sickness behavior response and modified sexual dimorphic responses: Possible model of Kabuki syndrome

The fundamental insights into the impact of impeller geometry on the gas helicity can help equipment suppliers to design more energy-efficient impellers while reducing the overall energy expenses of wastewater plants and aerobic fermenter. In this perspective, the proof of concept was developed using electrical resistance tomography and computational fluid dynamics (CFD) modelling. At a fixed speed ratio (central impeller rotational speed/ anchor rotational speed), the sign of gas helicity (+ or -) provides insights about the gas velocity direction and the degree of gas holdup in non-Newtonian fluid. The predicted gas holdup was within the range of experimental measurement. In this experiment, the carboxymethyl cellulose (1 wt% CMC) solution was used. It is a non-Newtonian fluid which obeys the power law model. The ASI impeller was the most energy-efficient impeller which generate reasonable aeration efficiency with negative helicity. The poor aeration efficiency of some novel impellers such as ASI Slanted and PBT Up-Down were attributed to the fluctuations in the gas helicity sign. The proof of concept shows that the local helicity analysis can be insightful to better understand gas-liquid mixing and further intensify gas dispersion. The lift force generated by these impellers can be useful for anaerobic digester.

Abstract # 4270 Glucocorticoid receptor sensitivity and stress predict motivated effort expenditure

The fundamental insights into the impact of impeller geometry on the gas helicity can help equipment suppliers to design more energy-efficient impellers while reducing the overall energy expenses of wastewater plants and aerobic fermenter. In this perspective, the proof of concept was developed using electrical resistance tomography and computational fluid dynamics (CFD) modelling. At a fixed speed ratio (central impeller rotational speed/ anchor rotational speed), the sign of gas helicity (+ or -) provides insights about the gas velocity direction and the degree of gas holdup in non-Newtonian fluid. The predicted gas holdup was within the range of experimental measurement. In this experiment, the carboxymethyl cellulose (1 wt% CMC) solution was used. It is a non-Newtonian fluid which obeys the power law model. The ASI impeller was the most energy-efficient impeller which generate reasonable aeration efficiency with negative helicity. The poor aeration efficiency of some novel impellers such as ASI Slanted and PBT Up-Down were attributed to the fluctuations in the gas helicity sign. The proof of concept shows that the local helicity analysis can be insightful to better understand gas-liquid mixing and further intensify gas dispersion. The lift force generated by these impellers can be useful for anaerobic digester.

Response surface optimization of Bambara nut kernel yield as affected by speed of rotation, and impeller configurations

Abstract The number of impeller slots, slot angle (angulations), and rotational speed are some of the operational parameters that influence kernel yield of centrifugal impact nut shellers. The effects of these three parameters on Bambara nut kernel extraction using a horizontal placed centrifugal Bambara nutcracker with a capacity of 150.6 kg/hr at a speed of 2200 rpm was determined using a split plot factorial experimental design. The dehulling efficiency increased with increase in rotational speed and number of impeller slots with a maximum value of 90.5% obtained at the highest speed of 2251 rpm, 75 ° angulations and 4 impeller slots while the minimum dehulling efficiency was 59% obtained at the lowest speed of 1125.8 rpm, 60 ° angulations, and 2 impeller slots. This range of values produced an extraction yield of 79.7– 84.5% and broken kernel of 11–59.6%. The results were fitted and responses were plotted and statistically analyzed to obtain the relationships between the variables. The optimum range of dehulling efficiency was 75.67–87.94% at rotational speed of 1956.42 -2135.74 rpm, angulations of 67.82 °–90 ° and 2–4 impeller slots. The optimum kernel yield ranged from 83.54–84.98% at 1125.8–1228.78 rpm, 47–90 ° and 2 -4 slots while the optimum kernel damage was 12.56 -15.19% at 1126.46–1131.3 rpm, 2–4 slots and 90 ° angulations. However, from the coefficient Table, it was only the speed and interaction of speed and angulations that significantly affected the nut dehulling efficiency and kernel yield respectively at p

Application of extended quadrature method of moments for simulation of bubbly flow and mass transfer in gas‐liquid stirred tanks

In the present paper, two gas‐liquid stirred tanks, one agitated by a radial impeller and another by an axial impeller, are modelled using the open‐source computational fluid dynamic (CFD) package OpenFOAM (open source field operation and manipulation). The combined effect of the bubble break‐up and coalescence in the tank is considered by a population balance model (PBM) called extended quadrature method of moments (EQMOM). The three‐dimensional simulation is made using a multiple reference frame (MRF), a well‐established method for the modelling of mixers. Dispersed gas and bubble dynamics in the turbulent flow are modelled using the Eulerian‐Eulerian approach (E‐E) with mixture k‐epsilon turbulent model and the modified Tomiyama drag coefficient for the momentum exchange. The model is developed to predict the spatial distribution of gas phase fraction, Sauter mean bubble diameter (), number density function (NDF), dissolved oxygen (DO) evolution, and flow structure. The numerical results are compared with experimental data and a fair agreement is achieved. The results of the axial impeller are discussed based on four impeller rotational speeds with different volumetric mass transfer coefficients.

Discrete element method study of effects of the impeller configuration and operating conditions on particle mixing in a cylindrical mixer

We employed the discrete element method to study the effects of the impeller configuration (i.e., blade diameter, inclination angle, and blade number), rotational speed, and fill level on the flow and mixing of particles in a cylindrical mixer equipped with flat and inclined blades. The coefficient of rolling friction, coefficient of static friction, and coefficient of restitution were experimentally determined before the simulation, and simulation results of the torque and surface particle distribution were validated in experiments, particularly when using a true Young’s modulus in the discrete element method. The performance of the mixer was assessed using the Lacey mixing index. The input work per unit volume was used to represent the mixing efficiency. The circumferential velocity and axial diffusion coefficient of the particles were quantitatively analyzed to reveal the effect of particle flow on the mixing. It was found that the mixing performance and efficiency of a three-blade mixer are better than those of two- and four-blade mixers. For pitched blades, a three-flat-blade mixer has better mixing performance than a three-45°-blade own-pumping or a three-45°-blade up-pumping mixer, but the mixing efficiency of the three-45°-blade up-pumping mixer is the best among these three mixers. As the rotational speed increases, the mixing performance improves but the mixing efficiency hardly changes. When the fill level is 0.4 times the cylinder diameter, the 160D two-flat-blade mixer has good mixing performance with high mixing efficiency. The circumferential velocity has the greatest effect on mixing performance for side-by-side initial loading.