Multistage Impeller Research Articles

Structural Analysis and Optimization of Ultra-High-Speed Centrifugal Pump Rotor System Considering Fluid–Structure Interaction

An ultra-high-speed centrifugal pump plays a crucial role as part of an aircraft engine’s fuel supply system. This paper focuses on the coupled vibration and optimization of a parallel double-stage ultra-high-speed centrifugal pump considering fluid–structure interaction (FSI). The accuracy of the numerical calculation is verified and compared with the experimental results. The steady and transient characteristics of the rotor system are analyzed to ensure the operational reliability of the rotor system. Moreover, an orthogonal test is conducted to explore the transient structural characteristics of the rotor system. The existing cross-support structure meets high-speed stability requirements and there is no resonance in the cantilevered rotor system. The maximum and minimum errors for the head of Pump 2 are 4% and 0.7%, respectively. The minimum values for maximum average deformation and maximum average stress are less than 0.31 mm and 245 MPa, respectively, at design conditions. The position of Bearing 1 near the multi-stage impeller has the greatest impact on the deformation and stress of the rotor system, and the deformation and stress increase as the distance increases. The results of this study can provide a valuable reference for the design of ultra-high-speed centrifugal pump rotor systems.

CFD Analysis of Industrial Multi-Stage Impeller in Stirred Tank with Fractal Pattern Baffled and Impeller

This paper presents tool for analysis of CFD adapted for flows in multi-staged stirred vessels with fractal pattern baffled for industrial. In order to develop a good mixing process model for stirred tanks, several way have been investigated by using the computational fluid dynamic. Implementing fractal design into stirred tank’s baffle and impeller are believed to influence the flow characteristic inside the stirred tank. The mixing process will be conduct by using multi-stage stirred tanks. Hence, the study is to simulate a fractal pattern baffled stirred vessels with fractal base of impeller. Four models with a new concept and different design of stirred tank have been introduced and studied. The multi-stages stirred tanks will adapted with fractal base pattern concept. The simulation is carry out by using the standard k-ε turbulence model. The results have been analysis in order to prove that which one of that model is the most effective in mixing. The flows produced in stirred tank are different and relevant with each model. The velocity profiles also give a relevant and quite impressive result by each model. At the end, the results will be examined and compared with each data that use a common type of baffle and impeller design.

Heat transfer in a jacketed agitated vessel equipped with multistage impellers

AbstractIn this work, heat transfer via the cylindrical part of the jacket in an agitated vessel has been investigated. Heat transfer coefficients were determined using the transient method based on measuring the temperature dependency of the liquid batch on time. A multistage impeller made of two impellers was used in a cylindrical vessel with dished bottom. The lower impeller was a curved blade turbine with the diameter of d = 100 mm and the upper impeller was either a pitched three-blade or pitched four-blade impeller with the diameter of d

Analysis of heat transfer in a vessel with helical pipe coil and multistage impeller

AbstractResults of heat transfer coefficient measurements in an agitated vessel heated or cooled by the liquid media flowing in a helical pipe coil are presented in this paper. The multistage impeller made of two pitched six‐blade impellers and adjustable clearance was used in a vessel with conical bottom. The transient method based on measuring the temperature dependency on time and solving the unsteady enthalpy balance was used to determine the heat transfer coefficients between the agitated liquid and the helical pipe coil. The results are summarized by the Nusselt number correlations, which describe the dependency on the impeller Reynolds number. The second part of this paper introduces a theoretical analysis of the flow in the liquid batch near the helical pipe coil. Based on the known pumping capacity of the multistage impeller, the characteristic velocity near the helical pipe coil can be evaluated. This characteristic velocity can be then used to determine the Nusselt number describing the heat transfer in a flow around a cylinder with the same cross‐section profile as the helical pipe coil. A clear correlation between this Nusselt number and the integral Nusselt number is presented in this paper and introduces an alternative approach for prediction of heat transfer characteristics on the basis of hydrodynamic parameters describing an agitated system.

Pumping Capacity of Pitched Blade Multi-Stage Impellers

Abstract This paper extends knowledge about flow in an agitated batch with pitched blade multi-stage impellers. Effects of various geometrical parameters (blade number, distance between impellers) of pitched blade multi-stage impellers on pumping ability have been investigated. Axial velocity profiles were measured by LDA (Laser Doppler Anemometry). Axial pumping capacities were obtained by integration of measured axial velocity profiles in outflow from impellers. Main attention was focused on the effect of the distance between impellers in multi-stage configurations, on their pumping capacity and flow in the mixing bath in comparison with an independently operating pitched blade impeller with the same geometry. In case of a relatively close distance between impellers H3/d = 0.5 - 0.75, the multi-stage impeller creates only one circulation loop and the impellers itself behave identically as pumps in series. However for relative higher distance of impellers than H3/d = 1.25, the multi-stage impeller creates two separated circulation loops.

Numerical assessment on improving multistage centrifugal impeller performance by changing inlet skew angle at impeller inlet

Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics. The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet. Four variations of lean angles, that is, 8°, 10°, 15° and 20°, were made at first stage impeller. Reynolds Average Navier Stokes equation was used in simulation together with a shear-stress transport (SST) k-w turbulence model and mixing-plane approach, respectively. Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required. A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow. The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage, which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller. The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained.

Prediction of drop sizes for liquid–liquid systems in stirred slim reactors—Part II: Multi stage impellers

Based on the successful predictions of transient drop sizes in the first part of this research (Maaß et al., Prediction of drop sizes for liquid–liquid systems in stirred slim reactors—part I: single stage impellers. Chem. Eng. J., 162 (2010) 792–801), this part is a straight continuation and extension of the earlier work. The predictive capabilities of the used population balance equation model are increased for single stage impellers and transferred to scale-up procedures of such applications. Therefore different scale-up rules for liquid–liquid systems are tested experimentally and by simulations in two different sized, geometrically similar vessels. The multi stage impellers are tested against comparable single stage impellers in terms of power consumption, mixing time and minimum impeller speed. Especially for high aspect ratios (larger than three), multi stage impellers successfully compete with the single stage ones. The measured drop size distributions in slim reactors with multi stage impellers showed no dependency on the local position, although the dispersion process is tedious due to the compartmentalization. The simulations are not able to reflect this initial phase of the dispersion process, but are in close agreement with the experiments after complete dispersion is fulfilled. Based on these experiences the aspect ratio is increased up to five and the resulting drop size can be predicted with reasonable deviations (lower than 10%). The results of the scale-up of this multi stage impeller liquid–liquid system do not lead to a clear conclusion. Although the simulations recommend the use of constant power input, the experiments could not support this. None of the other traditional scale-up rule are supported by the experiments. Overall, the results of power consumption, mixing time and dispersion behavior show the great potential of multi stage impellers for process optimization and intensification in slim reactors.

Centrifugal Force Based Magnetic Micro-Pump Driven by Rotating Magnetic Fields

This paper presents a centrifugal force based magnetic micro-pump for the pumping of blood. Most blood pumps are driven by an electrical motor with wired control. To develop a wireless and battery-free blood pump, the proposed pump is controlled by external rotating magnetic fields with a synchronized impeller. Synchronization occurs because the rotor is divided into multi-stage impeller parts and NdFeB permanent magnet. Finally, liquid is discharged by the centrifugal force of multi-stage impeller. The proposed pump length is 30 mm long and19 mm in diameter which much smaller than currently pumps; however, its pumping ability satisfies the requirement for a blood pump. The maximum pressure is 120 mmHg and the maximum flow rate is 5000ml/min at 100 Hz. The advantage of the proposed pump is that the general mechanical problems of a normal blood pump are eliminated by the proposed driving mechanism.

Development and Mixing Characteristics of a Multistage Impeller for Agitating Highly Viscous Fluids.

A new multistage impeller developed for mixing highly viscous fluids (0.1-10.0 Pa.s) in a stirred tank provides several advantages: excellent axial circulation flow, hardly any stagnant zones, and low power consumption. The impeller is composed of a vertical rotating shaft to which are attached, from top to bottom, a pair of two-bladed gate-impellers and one two-bladed paddle impeller. Four baffles are employed to accelerate the axial circulation flow in the tank. In this paper, the geometrical configuration of the multistage impeller is described, and its mixing characteristics for fluids of high viscosity - i.e. the power consumption, flow pattern, mixing time, circulation time, and mixing efficiency - are clarified. For comparison, the same characteristics were also examined in the stirred tanks using anchor, double-helical ribbon, and single-gate impellers. The results showed the multistage impeller to be superior to the other types in that the time required for complete mixing is relatively short and almost no stagnant zones are created. The relationship between the Reynolds and Nusselt numbers for the multistage impeller, as well as for single-gate and four-pitched paddle impellers, was clarified from the laminar to turbulent regions.