Standard Impeller Research Articles

Insights into the fluid dynamics of the Bach impeller

The Bach impeller is a novel impeller that was purposefully designed to reduce power consumption as well as shear stress levels in stirred bioreactors. Contrary to conventional impellers where stirring is achieved by the pushing action of the blades, the Bach impeller relies on a central spiral element which induces an up-pumping central vortex and discharges the flow in the tangential direction through vanes. This feature is new and relevant to the field of biochemical engineering where cell culture and microbial fermentation often make use of shear-sensitive, living organisms to produce biopharmaceuticals and medicines. This article offers a thorough characterisation of the fluid mechanics of this impeller by means of 2D phased- and time-resolved particle image velocimetry (PIV) experiments. Key flow dynamics parameters including velocity magnitudes, kinetic energy, and shear stresses were estimated for different combinations of impeller size, clearance, and speed. The standard impeller size, D/T=0.52, performed most promisingly in combination with an off-bottom clearance of C=0.6 T, as the elevated impeller height allowed to pull high momentum fluid to the upper part of the tank and therefore improved overall transport phenomena in the entire reactor volume. For this impeller diameter-clearance combination peak ensemble-averaged shear stresses at the vessel base were lower due to the impeller greater distance from the bottom. A distinctive feature of the Bach impeller was its "smooth operation" mode, where velocity fluctuations due to the vane passages are nearly negligible (∼5 % of ensemble-averaged kinetic energy). These aspects make of the Bach impeller an appealing option in the context of stem cell bioprocess applications.

Axial impeller with large surface blades optimized for wastewater treatment

Two variants of a four-blade axial impeller with diagonally rounded large-surface blades have been developed in order to reach two goals. First, the impeller should be hydrodynamically optimized for coagulation and flocculation processes (wastewater treatment), and second, the manufacturing severity and costs should be low (easily manufacturable impeller). The main process characteristics (power characteristics, blending characteristics, and hydrodynamic characteristics) of both variants of the impeller have been performed in various vessel-to-impeller configurations and the results are presented in the paper. The obtained values were compared with other standard impellers and TECHMIX hydrofoil impellers, and it was found that one of the proposed variants (4TR10) seems to be a perspective hydrofoil impeller for blending processes in the chemical, pharmaceutical, or mining industry. The coagulation/flocculation performance of the impeller has been tested and the results proved that the impeller produces the highest ratio of macroaggregates and the lowest ratio of non-aggregated particles compared to standard impellers.

G-Reactor at Micro-Plan

The stirrer reactor govern the industrial pharmaceutical productions up to the present, however the complex transmission systems may increase the costs exponentially with the power rates and the hermetic rector sealing. G-reactor improves the analogous reactors with simple pneumatic power device to heavy duty performances at high technological risks by pathogens and per substitution of complex transmissions by own-design; a single compression unit produces the sterile air to the power input of micro-plants and the oxygen of aerobic processes; important economic technical profits is foreseen; microplants distinguishes by small installations for compressed air and the services with overall automatic control available; the reliable performance for the human health, variable speed and standard impeller system, simple sterilization, safe sampling and supplies, foam-breaks to avoiding chemicals and simple automatic flow control distinguish the installations. The mathematical simulation of G-reactor performances to the mixing operations at gas-liquid systems to mass-transfer is shown; a solved example to a specific process illustrates the calculus fundamentals; the software enables the calculus of consumption parameters to the reactor scale-up and micro-plants of maximum capacity; the descriptive data analysis is discussed for the primary technical evaluations and general conclusions. The innovation is proposed for the small production scale of drugs and the unit operations of the chemical industry; a brief technical description of micro-plants and the production of sterile air may lead to the process engineering and the preliminary analysis of costs. The prophylactic treatment of the residual gas flow is shown.

Numerical and Experimental Study of the Impeller of a Liquid Pump or a Truck Cooling System and the Development of a New Technological Open-Type Impeller

Typically, closed-type impellers are more efficient than open-type impellers, but in the manufacture of closed-type impeller, cost of wheels is higher. This paper describes the development of cost-effective and simple impeller wheel for a fluid pump in the truck cooling system. To perform this task, the numerical computations of a standard impeller wheel were carried out, its characteristics were also obtained from a test bench, the standard impeller wheel model was verified. The open-type impeller wheel was developed according to the current dimensions of standard impeller wheel and then analyzed with the numerical computations by the software ANSYS CFX (Academic license) computational fluid dynamics. The developed open-type impeller wheel works very effectively in spite of performance degradation by 5% in comparison to the closed-type impeller wheel. When working as a part of engine, the pump efficiency is 0.552-0.579. The maximum value of the pump efficiency is 0.579, it can be achieved at the highest speed of the pump (4,548 rpm and 655 l/min)

Numerical and Experimental Study of the Impeller of a Liquid Pump of a Truck Cooling System and the Development of a New Open-Type Impeller

Typically, closed-type impellers are more efficient than open-type impellers, but in the manufacture of closed-type impellers, cost of wheels is higher. This paper describes the development of cost-effective and simple impeller wheel for a fluid pump in the truck cooling system. To perform this task, the numerical computations of a standard impeller wheel were carried out, its characteristics were also obtained from a test bench, the standard impeller wheel model was verified. The open-type impeller wheel was developed according to the current dimensions of standard impeller wheel and then analyzed with the numerical computations by the software ANSYS CFX (Academic license) computational fluid dynamics. The developed open-type impeller wheel works very effectively in spite of performance degradation by 5% in comparison to the closed-type impeller wheel. When working as a part of engine, the pump efficiency is 0.552-0.579. The maximum value of the pump efficiency is 0.579, it can be achieved at the highest speed of the pump (4,548 rpm and 655 l/min).

Centrifugal fan with inclined blades for vacuum cleaner motor

Centrifugal fans have several technical applications. Their aerodynamic performance is well-optimized nowadays, but the same does not apply to their acoustic performance. Noise control studies of centrifugal fans are often focused on designed operating conditions or operating conditions close to the onset of instability. This paper seeks to find an alternative geometry of the centrifugal fan impeller which would improve noise control of centrifugal fans in a wide range of operating conditions. In this paper, the term noise control refers to noise level reduction and additionally to manipulating the psychoacoustic properties of noise.The experimental work and numerical calculations focus on the centrifugal fan in vacuum cleaners. The experimental work, based on numerical simulations, is described to investigate the influence of the triangular cross section on the flow channel, formed by two inclined blades in opposite directions, on aerodynamic properties and the psychoacoustic performance of the impeller. The study demonstrates that impellers with a triangular flow channel achieve an aerodynamic performance which is comparable to that of standard impellers. The results also show that impellers with inclined blades deliver superior results in psychoacoustic metrics compared to impellers with upright blades.

Effect of operating parameters on fine particle grinding in a vertically stirred media mill

ABSTRACTThis article evaluates the effects of operating parameters on fine particle grinding process with a vertically stirred media mill. The effects are investigated through size reduction under different operating conditions by changing solids content, tip speed and the configuration of the impeller. Solids content at 65% (w/w) is demonstrated to be more efficient than 75% (w/w). The maximum difference in product size () is about 2 . Velocity maps are described at tip speeds of 5.23 m/s, 6.54 m/s and 9.81 m/s by positron emission particle tracking (PEPT). The lower tip speed saves the specific energy 50–100 kWh/t. Over energy input 100–300 kWh/t, of product is reduced 1–2 by replacing standard impeller with new types of impeller.

Numerical Investigation of Short Blades Effect on the Performance of a Centrifugal Pump

Improvement performance of centrifugal pumps is critical to reduce the consumption of electrical energy. One to improve the performance is to break down the circulation near the impeller exit. This can be achieved through the use of shorted blades. Effect of different sizes of shorted blade on pump performance is studied theoretically in this research which, test rig for testing centrifugal pump with standard impeller is constructed. Three impeller configurations with different size shorted blade are installed. The head, flow rate and shaft power are measured at 1500 rotational speed for the standard pump only. Also computational model using “Fluent” under ANSYS is constructed to predict the performance parameters of centrifugal pumps and to analyze the flow field in the impellers’ passages. Standard impeller (A) and three impellers configuration with different shorted blade length of 0.25 (configuration B), 0.2 (configuration C), and 0.15 (configuration D) of the full blade length are analyzed. Computational results show a reduction in flow circulation for all shorted blades impeller comparing to standard impeller. Also static pressure distributions at impeller exit become more uniform for impeller with 0.25, 0.2, and 0.15 shorted blades. The present work proves that the length of short blades have different effects for all pump cases. The best performance in this study occurred when shorted blades have length 25% from the original blade length. So when the effect of shorted blades is needed to study, each case of centrifugal pump should be investigated separately.

EFFECT OF ADDING SHORT BLADES ON CENTRIFUGAL PUMP PERFORMANCE AND DYNAMIC STABILITY

Centrifugal pumps are used extensively for hydraulic transportation of liquids over short to medium distance through pipelines where the requirements of head and discharge are moderate. The improvement of centrifugal pumps characteristics is important reduce the consumption of energy. One possible modification is to break down the circulation near the impeller exit using shorted blades. Numerical simulation and experimental verification are used to investigate the effects of short baled geometry on flow field and dynamic analysis of centrifugal pump. The model pump has a design specific speed of 23.75 rpm and an impeller with 7 blades. The short blade length factor Lb ratio varied from 0.16, 0.25 and 0.3 respectively from the impeller blade length. Other geometric parameters are kept constant. The inner flow fields and characteristics of the centrifugal pumps with different short blade lengths are simulated and predicted using commercial code Fluent under Ansys Ver.14.5. A test rig for testing centrifugal pump with standard impeller and three impellers of different shorted blade sizes is constructed. The head, flow rate and shaft power are evaluated for each pump configuration to show the effect of these shorted blades sizes on pump performance. When add short blades, with length ratio Lb=0.25, the vibration level increased to reach 1.32 mm/s. A 30% increase in vibration level is found compared to impeller without short blades; whoever, vibration level is still within the allowable level according to the international standards (ISO 10816-3). High frequency analysis shows that, the bearing is affected by adding short blades. For impeller with additional short blades between the main blades, H increased by 3.78 m(11.68%), and η by (6.95%). The power consumption in the case of blade length ratio Lb=0.25 approximately constant compared with the total energy consumption without impeller short blades with no power saving. Time averaged numerical results are compared with the experimental performance curve and good agreement has been achieved

Numerical study of flow field on molten iron desulfurization with mechanical stirring

The flow field of molten iron in the desulfurization process utilizing the mechanical stirring method under three different conditions was investigated using numerical simulation. The three conditions were central and eccentric stirring with the standard impeller and central stirring with the worn impeller, respectively. Three 1/20-scale numerical models were established and four inspection regions were set up on them. In all, 600 sets of instantaneous velocity fields for each model were exported and proper orthogonal decomposition technique was applied to deal with the data. The macroscopic flow field in the normal model operating under standard conditions was analyzed, which found that the mean flow has a relatively large fluctuation in flow field despite having a high proportion in total kinetic energy. A steady close relationship was revealed between the first two modes by studying the correlation of their coefficients. The first four modes were comparatively analyzed, which reflected that the change in the mean flow in the ladle using a worn impeller is slow and eccentric stirring is beneficial to desulfurization due to the asymmetry of the flow field on two sides.

Effect of number of branches on the performance of fractal impeller in a stirred tank: Mixing and hydrodynamics

Number of blades of an impeller, impeller design and its positioning in a stirred tank is known to affect the mixing in a stirred tank reactor. The extent of non-uniformity in mixing from conventional impellers can be reduced significantly using a space-filling impeller like a fractal impeller. In this work, we report the effect of number of branches (and hence the number of blades) of fractal impeller on power consumption, mixing and hydrodynamics. Velocity measurements were carried out using ultrasonic velocity profiler (UVP). Measurements showed that the performance of fractal impeller with different configuration is equivalent, however, better than standard impellers in terms of mixing achieved per unit power consumption. No significant difference was observed in radial and axial mean velocity profiles for three different configurations. However, the tangential velocity was found higher for four branches than two and three branches FI. Two distinct circulation loops were observed in upper as well as lower half of the vessel in r–z plane. Strong tangential flow throughout the baffled vessel helps to achieve good mixing even at low rotational speeds.

Study of fluid flow in baffled vessels stirred by a Rushton standard impeller

The paper deals with an investigation of velocity field in a tank stirred by a standard Rushton impeller located in the middle of the tank height. Time-resolved PIV method was used to measure the angle-resolved velocity field near the impeller blades in horizontal and vertical planes as well. Based on a simplified criterion λ2 < 0 the location, size and strength of trailing vortices behind the blades were determined. The measurements were carried out in two tanks of diameters T = 0.3 and 0.4 m and at mixing Reynolds numbers in a range 3.3–4.9 × 104. Simultaneously a detached eddy simulation (DES) was performed for the tank diameter T = 0.3 m and rotation speed 200 rpm (ReM = 3.3 × 104). The simulation results are compared with the experimental data.

High-titer ethanol production from simultaneous saccharification and fermentation using a continuous feeding system

A high-solid loading of lignocellulosic biomass in hydrolysis and simultaneous saccharification and fermentation (SSF) processes would make biofuel production more economical. However, several bottlenecks are determined by biomass characteristics, such as absorptiveness. We investigated the enzymatic digestibility and fermentability of pretreated Miscanthus as a high-concentration biomass in an SSF process, using a continuous feeding system and a particular type of impeller. When prehydrolysis and SSF was performed with a 25% dry solid loading, containing 30FPU/g cellulose, for 56h, 63.4±1.0g/L ethanol was produced with a standard impeller, while 69.2±1.6g/L ethanol was produced with an angled-type of impeller. Ethanol was produced in a short time, and ethanol productivity was enhanced, by using the continuous feeding system and an impeller angled at 30°. These findings contribute to the development of a continuous-production process for obtaining bioethanol from lignocellulosic biomass.

CFD Simulation of the Discharge Flow from Standard Rushton Impeller

The radial discharge jet from the standard Rushton turbine was investigated by the CFD calculations and compared with results from the Laser Doppler Anemometry (LDA) measurements. The Large Eddy Simulation (LES) approach was employed with Sliding Mesh (SM) model of the impeller motion. The obtained velocity profiles of the mean ensemble-averaged velocity and r.m.s. values of the fluctuating velocity were compared in several distances from the impeller blades. The calculated values of mean ensemble-averaged velocities are rather in good agreement with the measured ones as well as the derived power number from calculations. However, the values of fluctuating velocities are obviously lower from LES calculations than from LDA measurements.

BLENDING CHARACTERISTICS OF HIGH-SPEED ROTARY IMPELLERS

Abstract This paper presents a comparison of the blending efficiency of eight high-speed rotary impellers in a fully baffled cylindrical vessel under the turbulent flow regime of agitated charge. Results of carried out experiments (blending time and impeller power input) confirm that the down pumping axial flow impellers exhibit better blending efficiency than the high-speed rotary impellers with prevailing radial discharge flow. It follows from presented results that, especially for large scale industrial realisations, the axial flow impellers with profiled blades bring maximum energy savings in comparison with the standard impellers with inclined flat blades (pitched blade impellers).

Preliminary results of impeller design modifications

Power consumption in the oil mixing process is very much affected by the impeller design. Minor modification on the impeller design might result in better mixing and less energy consumption. This paper reports an early stage of applying the observation technique to modify three standard impellers, namely the Pitched blade turbine impeller, the CHEMSHEAR impeller and the Vertical Flat-Blade Turbine Impeller. The advantages and disadvantages of these three impellers were analyzed; accordingly minor modification on the impeller design is adopted. The CFD tool is used to evaluate one of the modified impellers; results indicated that the modified impeller achieves better fluid dispersion.

CFD simulation of flow patterns in unbaffled stirred tank with CD-6 impeller

Understanding the flow in stirred vessels can be useful for a wide number of industrial applications. There is a wealth of numerical simulations of stirring vessels with standard impeller such as Rushton turbine and pitch blade turbine. Here, a CFD study has been performed to observe the spatial variations (angular, axial and radial) of hydrodynamics (velocity and turbulence field) in unbaffled stirred tank with Concave-bladed Disc turbine (CD-6) impeller. Three speeds (N=296, 638 &amp; 844.6 rpm) have been considered for this study. The angular variations of hydrodynamics of stirred tank were found very less as compared to axial and radial variations.

Study of Aluminum Degasification with Impeller-Injector Assisted by Physical Modeling

ABSTRACTA full-scale water physical model of a degassing unit is built and used to evaluate the performance of several impeller designs. Four impeller designs are tested: a) one smooth not commercial impeller for reference purposes, b) a commercial design by FOSECO®, called standard impeller in this work, c) a commercial design by FOSECO® with notches, and d) a new design proposed in this work. Since the physical model is easy and safe to operate, a full experimental design is performed to evaluate the effect of the most important process variables, such as impeller rotating speed, gas flow rate, impeller design and the point of gas injection (a conventional gas injection through the shaft and a novel method of injecting gas through the bottom of the ladle) on the kinetics of oxygen desorption of water which is similar to dehydrogenation of liquid aluminum. The new design of impeller proposed in this work shows the best performance in degassing of all impellers tested in this study. It is found that the rotor speed and its design are the most significant variables affecting degassing kinetics, and therefore the analysis of the existing commercial impeller designs may be useful to optimize the fluid dynamics of the process, which in turn would increase efficiency and productivity of the process. Finally, the novel gas injection method through the bottom, proposed by our own group, presents slightly faster degassing kinetics than the conventional injection of purge gas in the conventional way through the impeller.

Comments to “CFD simulation of stirred tanks: Comparison of turbulence models. Part I: Radial flow impellers” and “Part II: Axial flow impellers, multiple impellers and multiphase dispersions”

Iread with great interest, articles of Joshi et al. (2011a,b) “CFD Simulation of Stirred Tanks: Comparison of Turbulence Models. Part I: Radial Flow Impellers” and “Part II: Axial Flow Impellers, Multiple Impellers and Multiphase Dispersions.” The articles cover a valuable review and analysis of CFD simulation of turbulent flow of mechanically agitated liquid and two-(or more-) phase mixtures with two frequently used high-speed impellers: standard Rushton impeller (RT) and pitched blade down flow turbine (PBT). Analysis of individual CFD procedures is made on the basis of results of laser Doppler velocimetry (LDV) in agitated systems with both investigated impellers. The commented articles bring very useful pieces of knowledge for application of CFD simulation when projecting and designing equipment with high-speed impellers and give many useful advices both to researches and people in industrial praxis for successful research and development of devices with investigated agitators. For deeper understanding and following usage of published items it seems that some of them could be clarified and completed: Experimental LDV data of velocity profiles (axial, radial and tangential) are presented in the time – and ensemble – averaged form, i.e. the average-time velocity is obtained over 360◦ of impeller revolution (Schafer et al., 1998), in contradistinction to the angle-resolved form, where angular (tangential) coordinate between two adjacent impeller blades is taken into consideration. It is not quite clear how the results of CFD simulation were evaluated by the same way when compared with LDV ensembleaveraged data. Moreover each velocity profile in observed agitated system (cylindrical baffled vessel with axially located impeller) depends on tangential position of the radial ray where the experiments were carried out. It seems from Figure 4 (Joshi et al., 2011a) and Figure 1 (Joshi et al., 2011b) that location of experimental radial rays was between opposite baffles, but presented experimentally determined radial profiles of all three components of the mean ensemble-average velocities better correspond to the radial ray in the midplane between adjacent baffles. The authors of commented articles described design of both investigated impellers. For PBT 30, 45 and 60 they do not mention a number of their blades, nor relative width of the blade. For RT they mentioned “standard Rushton turbine” and it is hoped that this impeller has six blades and exhibits the standardized simplexes of geometric similarity. Nevertheless, the power input of RT mentioned in the article of Joshi et al. (2011a) depends significantly on the thickness of the RT disk t (Bujalski et al., 1987; Rutheford et al., 1996) according to the formula for the impeller power number:

Analysis of interaction between geometry and efficiency of impeller pump using rapid prototyping

Design aids available today might have helped the pump designers to bring about theoretically the most efficient pumps, but the production technology and quality control during manufacture has not kept pace with such achievements in realizing the goals of developing energy efficient pumps. Pump designers often face the problem of selecting and optimizing a number of independent geometrical parameters whilst aiming at the desired efficiency from the pump. The only option is to approximate the theoretical design with experimental findings iteratively until the end result is achieved. Tremendous development of advanced manufacturing technology and computer technology has made rapid prototyping and computational fluid dynamics (CFD) techniques the right alternative method of reaching the target. Centrifugal pump impeller geometry, which contributes maximum complexity in flow during pump design, has been analysed in this work based on the parameters derived through computer-aided design (CAD) and CFD analysis. Using selective laser sintering, technique the impeller designed by CAD and two standard impellers commercially available for the same duty requirement is manufactured and their performance is tested to know their hydraulic efficiency. Results obtained from this work are useful for standardising pump impeller design and for developing energy-efficient pumps.