Propeller Impeller Research Articles

Gas–liquid mixing performance of a non‐Newtonian fluid in a multiple‐impeller agitated tank

AbstractBACKGROUNDThis target is to decide power input and gas hold‐up for gas–liquid mixing aqueous CMC solutions. The analysis considers the impact by varying the impeller speed and gas flow rates in a stirred tank bioreactor of three kinds of multiple impellers. The effects of the impeller type, rheology, and operating conditions were investigated on power drawn, relative power demand (RPD), gas holdup, and volumetric mass transfer coefficient.RESULTCompared to the Rushton turbine (6RT) and 4‐pitch blade (4PBT) impeller, the propeller (3PP) impeller presented a minimal event of the gassing on the RPD. 4PBT impeller has shown a higher gas hold‐up compared to the Rushton turbine and propeller impellers. The aerated agitated tank was established a dimensionless correlation for the RPD as a function of flow number and web number. Besides, the gas–liquid agitated system was also introduced a dimensionless correlation to compute the overall gas hold‐up as a function of specific power consumption. For the maximum dispersion mixing intensity, the impeller structure with low RPD looks to be more adequate. Further, maximizing gas holdup in the structures with high RPD is advantageous. The effects of impeller speed, gas superficial velocity, and rheology on the volumetric mass transfer coefficient were examined.CONCLUSIONThe volumetric mass transfer coefficient increased with an increase in impeller speed, gas superficial velocity, and power consumption per unit volume and decreased as rheology increased. The averaged kLa for each multiple‐impeller was correlated well with the specific gassed power consumption and gas superficial velocity. © 2024 Society of Chemical Industry (SCI).

Multi-site Garbage Collection Robot based on Machine Vision

At present, the problem of garbage disposal has become an urgent problem to be solved in the global energy technology revolution and transformation and development. The mainstream garbage removal methods are manual picking and mechanical collection, which has low cleaning efficiency and high cleaning cost. In order to realize the convenient and efficient recycling and cleaning of land and water garbage, a new propeller dynamics model is proposed. Through the structural strength analysis and gas-liquid two-phase flow simulation analysis, combined with the aerodynamic theory, the propeller impeller model was optimized and its suitable working parameters were explored. Based on the paddle impeller mechanism, combined with the visual recognition and classification system controlled by the algorithm combining YOLO and template matching, a multi-site garbage recycling robot based on machine vision was designed, which realized the intelligent and multi-step integration of garbage recycling, and provided a new research idea for improving the way of garbage cleaning.

Structural improvement of propeller impellers of high-temperature and high-pressure reactor based on TRIZ theory

With the rapid development of science and technology, exploration and study of extreme environments have advanced significantly. Consequently, the demand for equipment designed to operate under these conditions has increased. This paper proposes an innovative design method for stirring impeller structures based on the Teoriya Resheniya Izobreatatelskikh Zadatch (TRIZ) theory. By analyzing the interaction between components during the stirring process, we establish a TRIZ conflict resolution-based model for the innovative design process of stirring impeller structures. Our innovative design process is model-led, based on the TRIZ conflict resolution theory. This process improves existing stirrer structures to design a new type of stirrer with an ultra-thin multi-cross-shaped hole structure. We compare our proposed structural model to an existing stirrer using Computational Fluid Dynamics (CFD) for numerical simulation. The effect of different thicknesses, numbers of holes, radii, and shapes of the frame stirrer on the flow field values was analyzed. The results indicate that reducing the stirrer thickness, increasing the number of holes, and perforating the stirring impeller can enhance its stirring capacity. Changing the opening radius and adding special-shaped holes to the stirring impeller can also modify its stirring capacity. Ultimately, the proposed frame stirrer with an ultra-thin multi-cross-shaped hole structure increases the maximum turbulence kinetic energy by 14.6% and the maximum speed by 32.9% compared to the existing stirrer. Studying the feasibility of this innovative model and design method can provide new ideas for designing high-temperature and high-pressure reactor impellers in extreme environments.

Energy Losses Assessment of Smallholder Farmers’ Surface Water Irrigation Pumps in South and Southeast Asia Using Entropy Generation Principle

One of the most serious problems among smallholder farmers in South and Southeast Asia associated with the use of a surface water irrigation pump is low engine performance. The main cause of this low performance is the decrease in the flow field energy conversion mechanism caused by irreversible processes. The energy conversion theory suggests that pump efficiency is maximum when the loss is minimum. Whatever the origin of the losses, the deterioration in engine performance is due to a deterioration in the reversibility of the pump system. In this study, the pump is classified as the propeller impeller (PI), the improved axial or typical impeller (TI), and the conical hollow-shaped impeller (CI). Entropy production is applied to the pump on design improvement and loss sources location and mechanisms. The entropy production consists of viscous dissipation and turbulent dissipation. In this study, the pump design improvement of various designs based on entropy production has been studied in detail to predict energy loss in areas such as the inlet section, impeller, or discharge pipe. With the entropy generation, the optimum efficiency of different pump designs CI, PI, and TI were determined. The results showed that in all designs, more than 63% of the total entropy generation came from turbulent distribution. The flow in the pumps was analyzed in detail in comparison with entropy generation. It was found that the entropy generation rate increased in the secondary flow direction and was consistent with free-stream velocity. The PI design at the inlet pipe should be modified for reducing flow separation and entropy generation. All design impellers showed high energy losses, especially near the hub and tip along the leading edge and trailing edge. Therefore, it is possible to determine which features of the flow and entropy generation are relevant to the pump improvement.

Mixing tank hydrodynamics and mixing efficiency for propeller impellers

In this study, the distribution of axial and radial velocities with the use of a PIV laser system was determined and the mixing power in a mixing tank with narrow and wide propeller impellers was measured. The pumping capacity and secondary circulation values in the mixing tank were calculated and on this basis, the energy efficiency of the operation of both types of propeller impellers was determined and compared with the efficiency of turbine impellers with inclined blades. It turned out that propeller impellers with wide blades are most effective as regards the amount of energy that should be supplied to the mixing tank to achieve the required mixing time. It was found that the share of pumping capacity in the total secondary circulation is almost twice as high as the share of induced circulation. Correlation equations for the dependence of the mixing power and dimensionless flow numbers on the pitch of the propeller blade were also formulated. All the results obtained were compared with the works of other authors. The paper also found that propeller impellers with a variable angle of inclination of the blade α depending on the current radius do not meet the theoretical assumption of a constant axial velocity of the liquid flowing out from of the impeller zone. For small radii of the impeller the explanation for this observation is the presence of the hub and shaft in the axis of the mixer and the effect of liquid slip for the steep agitator blades near the hub. For radii close to the radius of the stirrer, the reason is generation of induced circulation as the expense of the kinetic energy of the liquid flowing out of the impeller area.

Numerical Simulation and Process Enhancement of the Hydrolysis of 2-Chlorobenzal Chloride

Hydrolysis of 2-Chlorobenzal chloride is the primary production method of 2-chlobrobenzaldehyde in industry, but the reactor technologies and reaction processes of this method are traditional and underdeveloped, in which the dichotomous leaf hydrolysis agitator is commonly used, resulting in low efficiency during the hydrolysis process. In this article, ANSYS software was utilized to enhance the hydrolytic reactors used in industrial production by simulating and analyzing the dispersion characteristics of droplets in the reactor. The particle size distribution of dispersed phase droplets and the Sauter mean diameter (D32) were used to characterize the dispersion effect, and the dispersion characteristics of the dichotomous leaf agitator and the three-bladed back-curved impeller, three-bladed propeller impeller, open turbine impeller, and crescent impeller were compared and studied. The results showed that there was a log-linear relationship between the D32 of the dispersed phase and the stirring speed in different systems; the number of tiny droplets in the three-bladed back-curved impeller system increased remarkably, and the droplets size distribution width decreased significantly, achieving mass transfer enhancement in the hydrolysis reaction system. The reliability of the simulation results was verified by the measurement experiment using the Sauter mean diameter (D32) of dispersed phase droplets. The results showed that the Sauter mean diameter (D32) variation trend is consistent with that of the simulation, and the error between them is less than 10%. A lab-scale hydrolytic reactor was designed and produced based on the scheme of an industrial hydrolytic reactor equipped with a three-bladed back-curved impeller, the effect of the hydrolytic reaction was verified, and the process conditions were strengthened under the same conditions. The results showed that, compared with the case in the reactor using a dichotomous leaf hydrolysis agitator at the same reaction temperature and catalyst conditions, the reaction time of hydrolysis completion reduced to 58.33% at the lab-scale, and to 63.89% at the industrial-scale at the stirring rate of 446 r/min, using a three-bladed back-curved impeller. These results provide a technical scheme and a basis for process strengthening for improving the production efficiency of 2-chlorobenzaldehyde production equipment in industry.

Mixing performance of a non-Newtonian fluid in a coaxial agitated impeller reactor

BackgroundThe power demand and mixing performance of three different coaxial mixers, fitted with either a Cowles turbine, 4-pitched blade turbine or 3-blade propeller impeller as the inner element, and anchor impeller as the outer element, were evaluated in a counter rotating mode in the laminar, transition, and turbulent flow regimes. MethodsCMC solution (sodiumcarboxymethyl cellulose) was used as the non-Newtonian fluid. The quantitative correlations for CMC solutions were established to calculate the power draw and the mixing time of the three coaxial mixers. The inner agitators which produce axial flow were identified to be more efficient than those which produce radial flow. Significant findingsResults show that the 4-pitched blade turbine/anchor impeller is the optimized combination among the three coaxial mixers tested, providing the shortest mixing time given the same power consumption. Based on mixing efficiency criteria, this study confirmed that the 4-pitched blade turbine/anchor impeller counter-rotating mode consistently yields the best results in the full flow regimes.

Investigation on pH influence for the effective transportation of coal water slurry using experimental design

ABSTRACT The present study aims to identify the pH values in preparation of coal water slurry (CWS) that were evaluated. Rheological characteristics and stability of coal water slurry (CWS) were observed with two types of impellers at pH varying from 6.99 to 7.24. The results showed that the concentration of coal water slurry, rheological characteristics and stability of CWS for propeller and rushton impellers. The parameters that are most effected on the objectives are impeller speed (N) and ratio of clearance height with diameter of tank (C/T). The third parameter, ratio of slurry height with tank diameter (Z/T), is not effecting on output. The pH values of concentrated coal water slurry are favorable to transport to coal gasifier. For propeller impeller, the pH values vary from 6.99 to 7.15; for Rushton impeller pH values vary from 7.12 to 7.24 comparatively Rushton impeller having more base which is most favorable and obtain good CWS concentration. The influence of coal particle size is also investigated on pH values for optimal parameters of equipment.

Research on Key Process Technology for Profile Electrolytic Finishing of Large Marine Propeller Impeller

Abstract An electrolysis process method for free-form blade surface finishing is proposed for a free-form surface impeller, and a stepwise method is used to process the inter-blade channel of the overall impeller. The forming cathode is then used to finish the blade to meet the blade processing requirements. In the design, the forming cathode structure was improved by using motion simulation software, and the flow field simulation software was used to simulate and analyze the cathode flow channel. The cathode shape and the electrolyte flow rate between the electrodes meet the processing requirements. In the process of processing experiments, the motion path of the cathode was analyzed and optimized. The effect of the feed direction on the uneven distribution of the blade machining gap was reduced through optimization, and high-frequency pulse power processing was used to reduce the machining gap and improve the machining accuracy of the blade. The experimental results show that the process scheme is feasible and the precision of the processed impeller free-form surface is significantly improved. The material is a monolithic turbine disk of high-temperature alloys, and its large twisted blade processing has always been a problem in the manufacturing industry.

Determination of forced convection heat transfer coefficients and development of empirical correlations for milk in vessel with mechanical agitators.

Heating of milk is an important unit operation to produce many milk based products. This process is done either in heat exchangers or in agitated vessels, where the mode and type of heat transfer plays a significant role. Use of mechanical agitator with suitable impeller would result in uniform agitation of the liquid. Data for forced convection heat transfer coefficients for milk in agitated vessel have not been documented. In the present investigation, forced convection heat transfer coefficients for milk, using mechanical agitators in vessels have been determined. Experiments have been conducted in vessels (Baffled as well as Unbaffled vessel) that were designed and fabricated under standard procedure employing: (1) Flat Six Blade Turbine impeller, (2) Inclined Six Blade Turbine impeller, (3) Three Blade Propeller impeller and (4) Two Bladed Paddle. Heat transfer coefficients were determined for for cow milk (3.5% fat), standardised milk (4.5% fat) and full cream milk (6.0% fat). The Two Bladed Paddle was found to as yield the highest heat transfer coefficient for all three types of milk. In addition, empirical correlations for the forced convection heat transfer using have been developed for each case. These heat transfer correlations derived will find application in large scale design and the experimental setup would be useful for future investigation with different liquids and impellers.

Solid Particle Distribution in Centrifugal Impeller Contactors

The recently developed centrifugal impeller is examined to investigate the solid–liquid mixing in a mechanically agitated contactor. Using the sample withdrawal method, the effects of impeller geometrical parameters, impeller rotational speed (200–700 rpm), solid particle size (500–1100 µm), and solid loading (2–10 vol%) on the degree of homogeneity are studied. The axial and the radial solid concentration profiles and the minimum impeller speed for the complete homogenization are also determined. In comparison with a widely used propeller impeller, considerably higher homogeneity values in lower impeller speeds are obtained (90% homogeneity against 16% homogeneity at 200 rpm at the same conditions). Having also lower power consumption makes this a superior impeller in solid–liquid mixing processes especially in shear-sensitive systems.

Correlation of Power Consumption for Eccentric Rectangular Mixing Vessel with Propeller Impeller

Correlation of Power Consumption for Eccentric Rectangular Mixing Vessel with Propeller Impeller

Prediction of Mixing Pattern by Using Power Number Diagram in Baffled and Unbaffled Mixing Vessels

Mixing patterns generated in stirred vessels for a wide range of Reynolds numbers were observed using a decolorization method based on the reaction between sodium thiosulfate and iodine. A relationship was established between the power number diagram (NP–Re diagram) and the shape of the isolated zone was observed. At low Reynolds numbers (laminar regime), the isolated zone resembled a doughnut ring, while a cylindrically rotating zone isolated at high Reynolds numbers (turbulent regime). Even with a small change in Reynolds number, the doughnut-ring-shaped isolated zone suddenly changed to a cylindrically rotating zone in an unbaffled vessel. The cylindrically rotating zone was not observed in baffled vessels at high Reynolds numbers. The clearance between the propeller impeller and the vessel bottom brought about a change in the mixing patterns, although the power consumption the remained constant.

완전 혼화조를 이용한 폐수처리 공정의 응집특성

본 논문은 완전 혼화조를 이용한 폐수처리 공정의 응집특성에 대한 연구를 목적으로 한다. 완전 혼화조 시스템은 유체 저장조, 임펠러가 장착된 3단의 혼화 및 응집부, 응집보조제 및 응집제 주입부, 응집 침전조 그리고 제어부로 구성된다. 실험용 폐수는 터널 공사현장에서 폐수 슬러지를 수거하여 약 1,000NTU의 탁도를 갖도록 만들었다. 응집보조제의 주입량이 증가함에 따라 약 99% 정도까지 탁도 제거율이 증가하였으며, 응집제의 주입량이 일정한 범위 이상으로 증가하면 탁도 제거율이 감소하는 것을 알 수 있다.

Influence of the agitation rate on the treatment of partially soluble wastewater in anaerobic sequencing batch biofilm reactor

This work reports on the influence of the agitation rate on the organic matter degradation in an anaerobic sequencing batch reactor, containing biomass immobilized on 3 cm cubic polyurethane matrices, stirred mechanically and fed with partially soluble soymilk substrate with mean chemical oxygen demand (COD) of 974+/-70 mg l(-1). Hydrodynamic studies informed on the homogenization time under agitagion rates from 500 to 1100 rpm provided by three propeller impellers. It occurred very quickly compared to the total cycle time. The results showed that agitation provided good mixing and improved the overall organic matter consumption rates. A modified first-order kinetic model represented adequately the data in the entire range of agitation rate. The apparent first-order kinetic constant for suspended COD rose approximately 360% when the agitation rate was changed from 500 to 900 rpm, whereas the apparent first-order kinetic constant for soluble COD did not vary significantly.

Influence of liquid-phase mass transfer on the performance of a stirred anaerobic sequencing batch reactor containing immobilized biomass

This paper reports on the influence of the liquid-phase mass transfer on the performance of a stirred anaerobic sequencing batch reactor treating low-strength wastewater. The biomass was immobilized in cubical polyurethane foam particles (5 mm per side). The 4.2 l volume reactor was operated at a temperature of 30 °C. A synthetic substrate with a mean chemical oxygen demand (COD) of 560±53 mg/l was treated in 8 h cycles. A mean COD removal efficiency of 78±3% was achieved. Three propeller impellers were used to vary the agitation rate from 300 to 1100 rpm in order to evaluate the influence of the liquid-phase mass transfer on the reactor’s overall performance. The first-order kinetic model was found to represent the degradation of organic matter well, with an apparent constant of 0.54–1.5 h −1 and an agitation rate of 300–900 rpm. The concentration of residual substrate decreased significantly at agitation rates above 800 rpm. Thus, the liquid-phase mass transfer substantially affected both the reactor’s overall performance and the cycle time required for maximum efficiency.

Effect of agitation in the hydrogenation of castor oil

AbstractCastor oil was hydrogenated to evaluate the effect of agitation during hydrogenation. The turbine and propeller impellers were evaluated during hydrogenation of castor oil at various temperatures, pressures, and catalyst concentrations. The effect of impeller position in the agitator at definite oil depth was also evaluated. Hydrogenation of castor oil at 130°C, 2.0 kg/cm2 hydrogen gas pressure with 0.5% Ni catalyst for 6 h while using two turbine impellers fitted in an agitator, one close to the reactor bottom and another at a height just below the top oil layer, revolving at 350 rpm, resulted in a product of a iodine value of 4.1, hydroxyl value of 156.4, and slip point of 84°C.

Concentration in a suspension discharging from a mixed vessel

Theoretical model has been proposed for the calculation of concentration of a suspension discharging at the top from a mixed vessel. It has been assumed that no separation of solids occurs during sampling near the level and that the samples provide local values of concentration obeying the diffusional model. The model has been tested on experiments involving a cylindrical vessel with baffles mixed by a propeller impeller.

Transport phenomena under unsteady conditions in an agitated vessel

AbstractAn experimental study of transport phenomena at the wall of an agitated vessel with a propeller impeller under unsteady conditions is reported. The transient in heat transfer at the wall is caused by a step change in the speed of agitation from an initial static condition. The results are expressed in terms of a rise in modified “j‐factor” above the initial free convection value and the number of revolutions taken by the impeller from the start of agitation. Also, an attempt has been made to find an analogy beween heat and momentum transfer. Results are given for the power in terms of Euler number plotted against the impeller Reynolds number. An empirical expression is also given for the transient heat transfer considering the system as a pure first order one with time delay. A “time‐factor” constant which gives the number of impeller revolutions for 63.2% of the change from the initial to a final steady state is expressed as a function of impeller Reynolds number (102 to 106) and fluid Prandtl number (6 to 106).