Impeller Diameter Research Articles

CFD prediction of mean flow field and impeller capacity for pitched blade turbine

This work focused on exploring a computational fluid dynamics(CFD)method to predict the macro-mixing characteristics including the mean flow field and impeller capacity for a 45° down-pumping pitched blade turbine( PBT)in stirred tanks. Firstly, the three typical mean flow fields were investigated by virtue of three components of liquid velocity. Then the effects of impeller diameter(D)and off-bottom clearance(C)on both the mean flow field and three global macro-mixing parameters concerning impeller capacity were studied in detail. The changes of flow patterns with increasing C/D were predicted from these effects. The simulation results are consistent with the experimental results in published literature.

Intensification of the rate of diffusion controlled electrolytic oxidation of FeSO4 by turbulence promoters in a stirred tank reactor in relation to wastewater treatment

The rate of diffusion controlled anodic oxidation of FeSO4 in rectangular stirred tank reactor was studied under galvanostatic conditions, H2 gas was produced as a byproduct at the cathode of the divided reactor. The rate of anodic oxidation of FeSO4 at a lead anode was enhanced by using active cylindrical turbulence promoters attached to the anode. Variables studied were impeller rotation speed, diameter and spacing of the turbulence promoters. The presence of turbulence promoters on the anode surface was found to increase the rate of FeSO4 oxidation by a factor ranging from 1.02 to 3.4 and reduce electrical energy consumption by an amount ranging from 25 to 80% depending on the operating conditions compared to the flat plate anode. The efficiency of the turbulence promoters was found to increase with increasing promoter spacing and diameter. The role of O2 bubbles which evolve at the anode surface simultaneously with FeSO4 oxidation in enhancing the rate of mass transfer jointly with turbulence promoters was discussed. Importance of the present study for treating wastewater containing FeSO4 was highlighted. Processes that produce wastewater containing FeSO4 include removal of H2S from petroleum hydrorefining gases by Fe2(SO4)3 oxidation to sulfur, regeneration of printed circuit etching solution and iron removal from steel mills pickling waste solutions. The importance of the present results in producing H2 at lower energy consumption and the possibility of integrating the present cell with the process of petroleum hydrorefining was noted. Also the importance of the present results in using FeSO4 as anodic depolarizer to reduce the cell voltage and energy consumption in the electrowinning of heavy metals from waste water was outlined.

Influence of impeller diameter on overall gas dispersion properties in a sparged multi-impeller stirred tank

The impeller configuration with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers, identified as PDT+2CBY, was used in this study. The effect of the impeller diameter D, ranging from 0.30T to 0.40T (T as the tank diameter), on gas dispersion in a stirred tank of 0.48m diameter was investigated by experimental and CFD simulation methods. Power consumption and total gas holdup were measured for the same impeller configuration PDT+2CBY with four different D/T. Results show that with D/T increases from 0.30 to 0.40, the relative power demand (RPD) in a gas–liquid system decreases slightly. At low superficial gas velocity VS of 0.0078m·s−1, the gas holdup increases evidently with the increase of D/T. However, at high superficial gas velocity, the system with D/T=0.33 gets a good balance between the gas recirculation and liquid shearing rate, which resulted in the highest gas holdup among four different D/T. CFD simulation based on the two-fluid model along with the Population Balance Model (PBM) was used to investigate the effect of impeller diameter on the gas dispersion. The power consumption and total gas holdup predicted by CFD simulation were in reasonable agreement with the experimental data.

Experimental study by online measurement of the precipitation of nickel hydroxide: Effects of operating conditions

The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter of D=240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution (PSD) were investigated. d43 and PSD were measured online using a Malvern Insitec Liquid Process Sizer every 20s. It was found that d43 varied between 13μm and 26μm under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.

Design of a Gas–Liquid Unbaffled Stirred Tank with a Concave Blade Impeller

Experimental investigation of unbaffled multiphase (gas–liquid) stirred tanks is conducted with the use of a concave blade impeller to analyze mass transfer, gassed power, and gas holdup. The experiments are carried out with various impeller diameter to tank diameter ratios and impeller clearances. The design criterion for the mass transfer rate is proposed, and its prediction capability is found to be satisfactory. The results show that the gassed power is dependent on the impeller diameter to tank diameter ratio and impeller clearance. The design criteria for gassed power to ungassed power ratio and gas holdup are also introduced. Multiphase modeling is done by employing the computational fluid dynamics (CFD) techniques to observe the characteristic flow pattern transition and to carry out a qualitative analysis of the mass transfer rate.

G0500405 トモグラフィックPIVによる撹拌槽流れの全視野体積計測

We carried out phase-locked Tomographic PIV measurements in a square shaped, vertically-oriented water tank, in order to understand its general flow behavior and turbulence shear stress distributions in detail. The three-dimensional experiments are carried out at four different, 40 mm thick, vertical volume sheets. The water is stirred by a commercially available impeller, which has three symmetrical twisted blades. The impeller is rotated at the constant angular speed of 150 RPM. The Reynolds number of the flow, based on the blade's tip velocity and the impeller diameter, is 59400. In the present study, we carry out the flow measurements at two angular locations, so that the combined flow field would enable us to fully understand how the tip-generated vortices bend and diffuse in the flow domain. Exploring behavior of the tip-generated vortices are of prime interest to us, because the turbulence kinetic energy happens to be primarily concentrated inside these vortices.

1614 三段遠心ポンプのベーンドディフューザに生じる旋回失速と半径方向スラストの変動

In this study, the effect of the rotor axial offset and impeller-diffuser gap (smaller gap or larger gap) on the performances and the unsteady thrust forces of a three stage centrifugal pump were experimentally investigated. The change of the gap was realized by cutting an impeller diameter. By cutting the impeller diameter (larger gap) the positive slope of the head performance curve was observed in lower flow rates than 20% of design flow rate, while it was not observed with the smaller gap. In the flow rate range with the positive slope, the distinct pressure fluctuation with low frequency (14% of impeller rotation), measured at the inlet throat of diffuser vane, could be recognized, which was found to be caused by the diffuser rotating stall with 1 cell. The unsteady radial thrust force caused by the diffuser rotating stall was observed at the same time. The rotating stall was more significantly observed in the 3rd stage, which was probably because the test pump system employed the balancing drum for the thrust balancing device; the effective flow rate is larger in the 1st and 2nd stage diffusers than the 3rd one due to the leakage flow to the balancing drum just upstream of the 3rd stage diffuser.

Study on the Development of Two-Stage Centrifugal Blood Pump for Cardiopulmonary Support System

【In the cardiopulmonary support system with an ECMO (extracorporeal membrane oxygenation), a higher pump head is demanded for a blood pump. In order to realize a blood pump with higher pump head, higher anti-hemolysis and thrombosis performances, a study on the development of unprecedented multistage blood pump was conducted. In consideration of the application of the blood pump for pediatric patients, a miniature two-stage centrifugal blood pump with the impeller's diameter of 40mm was designed and the performance was examined in experiments and computations. Some useful knowledge for a design of the blood pump with higher anti-hemolysis and thrombosis performances was obtained.】

Influence of impeller diameter on local gas dispersion properties in a sparged multi-impeller stirred tank

Vertical distributions of local void fraction and bubble size in air–water dispersion system were measured with a dual conductivity probe in a fully baffled dished base stirred vessel with the diameter T of 0.48m, holding 0.134m3 liquid. The impeller combination with a six parabolic blade disk turbine below two down-pumping hydrofoil propellers, identified as PDT+2CBY, was used in this study. The effects of the impeller diameter D, ranging from 0.30T to 0.40T (corresponding to D/T from 0.30 to 0.40), on the local void fraction and bubble size were investigated by both experimental and CFD simulation methods. At low superficial gas velocity VS of 0.0077m·s−1, there is no obvious difference in the local void fraction distribution for all systems with different D/T. However, at high superficial gas velocity, the system with a D/T of 0.30 leads to higher local void fraction than systems with other D/T. There is no significant variation in the axial distribution of the Sauter mean bubble size for all the systems with different D/T at the same gas superficial velocity. CFD simulation based on the two-fluid model along with the population balance model (PBM) was used to investigate the effect of the impeller diameter on the gas–liquid flows. The local void fraction predicted by the numerical simulation approach was in reasonable agreement with the experimental data.

Predicting Power for a Scaled‐up Non‐Newtonian Biomass Slurry

AbstractHigh‐solids biomass slurries exhibit non‐Newtonian behavior with a yield stress and require high power input for mixing. The goals were to determine the effect of scale and geometry on power number P0, and estimate the power for mixing a pretreated biomass slurry in a 3.8 million L hydrolysis reactor of conventional design. A lab‐scale computational fluid dynamics model was validated against experimental data and then scaled up. A pitched‐blade turbine and A310 hydrofoil were tested for various geometric arrangements. Flow was transitional; laminar and turbulence models resulted in equivalent P0 which increased with scale. The ratio of impeller diameter to tank diameter affected P0 for both impellers, but impeller clearance to tank diameter affected P0 only for the A310. At least 2 MW is required to operate at this scale.

Effects of impeller diameter and rotational speed on performance of pump running in turbine mode

The major limitations of mini/micro hydropower schemes is the higher cost of small capacity hydro turbines. Also, it is very cumbersome, time consuming and expensive to develop the site specific turbines corresponding to local site conditions in mini/micro hydro range. In such plants, small centrifugal pumps can be used in turbine mode by running in the reverse direction. The efficiency of pump as turbines (PATs) is usually lower than the conventional hydro turbines; however, there may be substantial decrease in the capital cost of the plant.Hydropower plants usually runs at part load for several months in a year due to insufficient water availability for the power generation. The application range of PAT can be widened if its part load and/or maximum efficiency can be improved. In the present study, experimental investigations are carried out on centrifugal pump running in turbine mode to optimize its geometric and operational parameters e.g. impeller diameter and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500rpm with original (∅ 250mm), 10% trimmed (∅ 225mm) and 20% trimmed (∅ 200mm) impellers. Impeller trimming led to improvement in efficiency at part load operating conditions. The performance of PAT was found better at the lower speeds than that at the rated speed. The effects of blade rounding were studied in all the cases and it led to 3–4% rise in efficiency at rated speed with the original impeller. The empirical correlation is also developed for prediction of efficiency in terms of impeller diameter and rotational speed in non-dimensional form.

The flow field in a centrifugal pump with a large tongue gap and back blades

In this paper, the unsteady 3-D turbulent flow fields in an end-suction centrifugal pump with a vaneless volute are studied numerically at three different rotation speeds. The unshrouded impeller of the pump, as a reduced diameter version of the original full-size impeller, has five backswept blades and five pump-out blades. The results show that the flow rate and pressure vary with the rotational speed according to the similarity law, and the normalized internal flow fields at all speeds are very similar. Due to the reduced impeller diameter, the pump efficiency is relatively low. Flows discharged from the front and back blade passages interfere with each other and swirling motion exists in the volute. The pressure fluctuations on the casing wall near the impeller outlet are extracted, and their spectra show that the component at the blade passing frequency was prominent. This study sheds some light on the characteristics of the internal unsteady flow of a centrifugal pump at different rotational speeds, and forms a basis for future study of flow induced pump vibration and noise.

Added mass moment of inertia of centrifugal dredge pump impellers

During the design of dredge pumps and drivelines, a torsional vibration analysis is performed in order to determine the critical frequencies of the system. The analysis requires information about the centrifugal pump impeller mass moment of inertia. For the impeller itself this geometrical property can be determined very accurately, but the influence of the surrounding fluid on the impeller's mass moment of inertia is much less easy to determine. This paper addresses the influence of fluid on the mass moment of inertia of a centrifugal dredge pump impeller, that is, the added mass moment of inertia. It describes the design of a test set-up for measuring the added mass moment of inertia of scale model impellers. Then a series of experiments is conducted in which the impeller geometry is varied. The parameters of influence are the impeller width ratio, the ratio between the suction diameter and impeller diameter, the number of blades and the blade shape. Analysis of the data provides insight into the importance of the added mass moment of inertia to the dynamics of the pump. Furthermore, the data provide a base for an engineering formula for the added mass moment of inertia of centrifugal pump impellers.

Numerical investigation of impeller trimming effect on performance of an axial flow fan

To study the performance variations of an axial fan after impeller trimming, numerical simulations are executed under the following conditions: trimming quantity of 5%, 10%, and 15% of blade height, with tip clearance changed and unchanged. The effects of trimming quantity and tip clearance on flow field and performance of the axial fan are investigated, and formulae are presented for total pressure rise and flow rate ratio versus impeller diameter ratio and for operating points before and after impeller trimming. The simulated results show that the performance curves after impeller trimming tend to decline. Near the design flow rate, the performance of the fan with unchanged tip clearance is aerodynamically superior to that with changed tip clearance; the former deteriorates at a large flow rate. The margin of parameters provided by design units exceeding the actual operation requires the fan to normally operate to the left of the rated load, therefore, axial fans with tip clearance unchanged after impeller trimming have been found to maintain better performance. The equations, denoting total pressure rise ratio and flow rate ratio versus impeller diameter ratio are available to determine the trimming quantity according to actual requirements of operating points after impeller trimming.

Solid–Liquid Suspensions in Top-Covered Unbaffled Vessels: Influence of Particle Size, Liquid Viscosity, Impeller Size, and Clearance

Particle suspension in liquids is a unit operation commonly encountered in the process industry. Although it is usually carried out in baffled stirred tanks, there are some specific applications where the presence of baffles may be undesirable. In the present work solid–liquid suspensions are investigated in a radially stirred unbaffled tank provided with a top cover. The minimum impeller speed at which all solid particles get suspended (Njs) and the relevant power requirements (Pjs) are assessed. The dependence of these two parameters on physical properties (liquid viscosity, particle concentration, and size) and system geometrical configurations (impeller diameter and clearance) is investigated, and a correlation for the Njs estimation is proposed. Results mark some notable differences with respect to baffled tanks: Njs appears to be almost independent of particle diameter, a feature that may suggest the adoption of unbaffled tanks when large heavy particles are to be dealt with. Also, Njs was found to decrease as liquid viscosity increases, once again marking a favorable discrepancy with respect to baffled vessels. As concerns the system geometrical configuration, a tank stirred by a D = T/3 six-bladed Rushton turbine offset by T/3 from the tank bottom is found to be the most convenient configuration among those investigated in this work. Present results are finally compared with literature information on solids suspension in baffled or unsteadily agitated unbaffled systems. In both cases, top-covered unbaffled stirred vessels are found to be a convenient choice, provided that mixing times are not a controlling factor.

Experiments on the whirling of pitched blade impellers in baffled mixing vessels

The whirling characteristics of a 45° pitched-blade impeller (PBI) operating in a baffled mixing vessel were studied experimentally. Test conditions include different blade configurations, impeller sizes and rotational speeds. Experiments were conducted in three mixtures of water and glycerol, with and without baffles, operating in both clockwise and counterclockwise directions. Four different impellers were used: three, four-blade PBIs with diameter tank-diameter ratios of D/DT=12, 914, 57, and one six-blade PBI with D/DT=57. The smallest impeller spans half of the tank diameter as is standard in most industries. The larger diameter impellers being specific to the polymer production industry. Experiments were conducted at speeds up to 1.2 times the natural bending frequency of the rotor shaft assembly. Impeller orbits together with torsional vibrations were measured directly using high speed imaging and strain gauges mounted at the root of the shaft. The results indicated that the impeller motions were random and could be modelled as an axisymmetric normal distribution. The mean square response of the impeller׳s deflection was dependent on the rotational speed and the rotational direction of the impeller.

The Development of a Cross-Flow Fan for Electronic Devices Cooling with a Focus on Laptop Computers

The directive is to develop a new type of cross-flow fan for cooling electronic devices. First, the module is based on the 60X60X6mm fan and attempts to use several parameters to enhance the fan’s performance. The parameters considered here include blade number, angle of the blade, impeller diameter, divergent structure, and outlet area. Both numerical and experimental analyses are carried out on the cross-flow fan which was oriented horizontally. The ANSYS Fluent software is used in a 2D simulation to predict the heat transfer coefficient and the flow fields. Next, the flow and acoustic noise measurements are carried out at different parameters with the aid of AMCA and semi-anechoic chambers. The results show that when the outlet vent size is 70% of fan outside diameter the outcome is an enhanced fan performance of 12%. The optimal number of blades is 37. A block is inserted below the fan blade to improve the fan performance by 8%. The numerical and experimental values of air flow were plotted and found to be consistent. In summary, this study provides a systematic process to develop a cross-flow fan that can meet the requirements for thin and light laptop computers.

횡류형 터빈을 적용한 수직축 풍력발전시스템의 성능평가를 위한 실험 연구

본 최근 성장하고 있는 해상 풍력의 실험연구에서 풍동시험이 수직형 횡류 풍력발전시스템의 성능을 조사하기 위해 실시되었다. 풍동의 시험 부분은 제한된 크기로 인해 실제 풍력 발전의 입구 안내 베인을 약 1/5로 축소시켰고, 터빈 임펠러의 지름을 모형 임펠러의 1/2로 감소시켰다. 임펠러 블레이드 갯수는 풍력 발전 시스템의 출력에 대한 또 다른 중요한 변수이기 때문에 8개와 16개로 변경하여 시험하였다. 실험 분석 결과, 모형 풍력 터빈의 출력 제동력은 정격 풍속 12m/s에서 블레이드 갯수가 8개 보다 16개일 때 82% 출력이 증가된 278와트로 측정되었고, 정격 제동력은 정격 작동 조건에서 3.9kW로 계산되었다. In this experimental study for the current growing offshore wind, a wind tunnel test was conducted to examine the performance of the vertical-type cross-flow wind turbine power generation system. Due to the limited size of the test section of the wind tunnel, the inlet guide vane of the original wind power generation was scaled down to about 1/5 and the turbine impeller diameter was also reduced to 1/2 of the prototype impeller. The number of the impeller blade is another important parameter to the output power of the wind power generation system and the number was varied 8 and 16. From the analysis of the experimental result, the output brake power of the model wind turbine was measured as 278watts with the 16-blade at 12 m/s of the rated wind speed and the rated brake power of the prototype wind turbine is calculated to 3.9kW at the rated operating condition.

Scale-up model obtained from the rheological analysis of highly concentrated emulsions prepared at three scales

We examine the scale invariants in the preparation of highly concentrated w/o emulsions at different scales and in varying conditions. The emulsions are characterized using rheological parameters, owing to their highly elastic behavior. We first construct and validate empirical models to describe the rheological properties. These models yield a reasonable prediction of experimental data. We then build an empirical scale-up model, to predict the preparation and composition conditions that have to be kept constant at each scale to prepare the same emulsion. For this purpose, three preparation scales with geometric similarity are used. The parameter NDα, as a function of the stirring rate N, the scale (D, impeller diameter) and the exponent α (calculated empirically from the regression of all the experiments in the three scales), is defined as the scale invariant that needs to be optimized, once the dispersed phase of the emulsion, the surfactant concentration, and the dispersed phase addition time are set. As far as we know, no other study has obtained a scale invariant factor NDα for the preparation of highly concentrated emulsions prepared at three different scales, which covers all three scales, different addition times and surfactant concentrations. The power law exponent obtained seems to indicate that the scale-up criterion for this system is the power input per unit volume (P/V).

CFD Prediction of Effects of Impeller Design on Floating Solids Mixing in Stirred Tanks with Pitched Blade Turbines

Computational fluid dynamics (CFD) simulations were performed to study effects of the flow pattern on the mixing quality of floating solids in stirred tanks with up- and down-pumping pitched blade turbine (PBTU and PBTD). The variables about impeller design have influences in the flow pattern and four key ones, impeller diameter, clearance from tank bottom, blade angle and number, were investigated in this work. Euler–Euler multiphase model along with mixture k–ε turbulence model was adopted. The relative motion between rotating impeller and stationary baffles was modeled with the multiple reference frame (MRF) approach. The predicted results were compared and explained with the experimental or theoretical results in published literature. Qualitative and reasonable agreement was achieved.