Numerical Analysis of the Fluid Flow in the First Stage of a Two-Stage Centrifugal Pump With a Vaned Diffuser

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
H. Stel ◽  
G. D. L. Amaral ◽  
C. O. R. Negrão ◽  
S. Chiva ◽  
V. Estevam ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Flow Pattern ◽  
Centrifugal Pump ◽  
Pressure Rise ◽  
Single Equation ◽  
Two Stage ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Wide Range ◽  
Pump Head

This work presents a numerical investigation of the fluid flow in the first stage of a two-stage centrifugal pump with a vaned diffuser. A computational fluid dynamics (CFD) analysis is performed by using the ANSYS-CFX software for a wide range of volumetric flow rates and also for different rotor speeds. The numerical results are validated against measured values of pressure rise through the impeller and diffuser of the first stage with an overall good agreement. Nevertheless, not only the best efficiency point evaluated numerically is overestimated in comparison with the measured two-stage pump values but also the computed hydraulic efficiency of the first stage. Investigation of the flow pattern for different flow rates reveals that the flow becomes badly oriented for part-load conditions. In such cases, significant levels of turbulence and blade orientation effects are observed, mainly in the diffuser. In spite of different flow rates or rotor speeds, the flow pattern is quite similar if the flow dimensionless coefficient is kept constant, showing that classical similarity rules can be applied in this case. By using such rules, it was also possible to derive a single equation for the pump head to represent the whole operational range of the pump.

Numerical Simulation of the Flow in a Centrifugal Pump With a Vaned Diffuser

2011 ◽  
Author(s):  
Willian Segala ◽  
Henrique Stel ◽  
Vanessa Hungria ◽  
Rigoberto E. M. Morales ◽  
Sergio C. Vicent ◽  
...  
Keyword(s):  
Numerical Model ◽  
Centrifugal Pump ◽  
Single Stage ◽  
Computational Time ◽  
Periodic Regime ◽  
Two Stage ◽  
Vaned Diffuser ◽  
Similarity Relations ◽  
Wide Range ◽  
Good Agreement

This work presents a numerical investigation of the water flow in the first stage of a two-stage centrifugal pump with a vaned diffuser. The geometry consists of a pipe intake, a 8-blade impeller, a 12-blade diffuser and an outlet extension chamber. The numerical modeling comprises a transient rotorstator interface connection between the impeller and the other static domains, and it was implemented in the commercial code ANSYS-CFX. The numerical runs were carried out for four impeller speeds and a wide range of volumetric flow rates. The standard k-ε turbulence model was used. An experimental loop is also used to measure pump head values to validate the numerical approach. Comparison of numerical head values with the experimental data showed a good agreement. Similarity relations used for the numerical head values for different impeller speeds also shows good agreement within the range studied. A transient analysis of the pressure values at the impeller-diffuser interface showed that, using a steady state frozen rotor approximation as the initial condition for the transient calculation, generally no more than half of a complete impeller revolution is needed for the pump to achieve temporal periodicity. This numerical procedure saves significantly the computational time. Moreover, the numerical results confirm that, once the periodic regime is achieved, an azimuthal periodicity at each 90° interval is also achieved, just as expected from the 8-to-12 blades ratio between impeller and diffuser. Comparison of the numerical efficiencies of the single-stage pump with the experimental counterpart showed significant discrepancies. These must be related to the geometric simplifications of the numerical model and volumetric pressure losses of the real pump not included in the numerical model. Consequently, the Best Efficiency Point of the single-stage pump was found to be different from the two-stage assembly, and the flow field analysis apparently confirms this feature.

scholarly journals Prediction of Droplet Production Speed by Measuring the Droplet Spacing Fluctuations in a Flow-Focusing Microdroplet Generator

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 812 ◽  
Author(s):  
Wen Zeng ◽  
Dong Xiang ◽  
Hai Fu
Keyword(s):  
Fluid Flow ◽  
Efficient Method ◽  
Immiscible Fluids ◽  
Droplet Generation ◽  
Flow Focusing ◽  
Flow Conditions ◽  
Flow Rates ◽  
Wide Range ◽  
Droplet Production ◽  
Monodisperse Droplets

In a flow-focusing microdroplet generator, by changing the flow rates of the two immiscible fluids, production speed can be increased from tens to thousands of droplets per second. However, because of the nonlinearity of the flow-focusing microdroplet generator, the production speed of droplets is difficult to quantitatively study for the typical flow-focusing geometry. In this paper, we demonstrate an efficient method that can precisely predict the droplet production speed for a wide range of fluid flow rates. While monodisperse droplets are formed in the flow-focusing microchannel, droplet spacing as a function of time was measured experimentally. We discovered that droplet spacing changes periodically with time during each process of droplet generation. By comparing the frequency of droplet spacing fluctuations with the droplet production speed, precise predictions of droplet production speed can be obtained for different flow conditions in the flow-focusing microdroplet generator.

scholarly journals Analytical Solution for Heat Transfer in Electroosmotic Flow of a Carreau Fluid in a Wavy Microchannel

2019 ◽  
Vol 9 (20) ◽  
pp. 4359 ◽  
Author(s):  
Saima Noreen ◽  
Sadia Waheed ◽  
Abid Hussanan ◽  
Dianchen Lu
Keyword(s):  
Fluid Flow ◽  
Flow Pattern ◽  
Flow Rate ◽  
Electroosmotic Flow ◽  
Linear Problem ◽  
Perturbation Technique ◽  
Volumetric Flow Rate ◽  
Carreau Fluid ◽  
Long Wavelength ◽  
Wide Range

This article explores the heat and transport characteristics of electroosmotic flow augmented with peristaltic transport of incompressible Carreau fluid in a wavy microchannel. In order to determine the energy distribution, viscous dissipation is reckoned. Debye Hückel linearization and long wavelength assumptions are adopted. Resulting non-linear problem is analytically solved to examine the distribution and variation in velocity, temperature and volumetric flow rate within the Carreau fluid flow pattern through perturbation technique. This model is also suitable for a wide range of biological microfluidic applications and variation in velocity, temperature and volumetric flow rate within the Carreau fluid flow pattern.

Steady and Unsteady Radial Forces for a Centrifugal Pump With Impeller to Tongue Gap Variation

2005 ◽  
Vol 128 (3) ◽  
pp. 454-462 ◽  
Author(s):  
José González ◽  
Jorge Parrondo ◽  
Carlos Santolaria ◽  
Eduardo Blanco
Keyword(s):  
Centrifugal Pump ◽  
Numerical Results ◽  
Momentum Exchange ◽  
Unsteady Forces ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency ◽  
Wide Range ◽  
Radial Forces ◽  
Similarity Laws

Experimental and numerical studies are presented on the steady and unsteady radial forces produced in a single volute vaneless centrifugal pump. Experimentally, the unsteady pressure distributions were obtained using fast response pressure transducers. These measurements were compared with equivalent numerical results from a URANS calculation, using the commercial code FLUENT. Two impellers with different outlet diameters were tested for the same volute, with radial gaps between the blade and tongue of 10.0% and 15.8% of the impeller radius, for the bigger and smaller impeller diameters, respectively. Very often, pump manufacturers apply the similarity laws to this situation, but the measured specific speeds in this case were found to be slightly different. The steady radial forces for the two impellers were calculated from both the measured average pressure field and the model over a wide range of flow rates in order to fully characterize the pump behavior. Again, a deviation from the expected values applying the similarity laws was found. The data from the pressure fluctuation measurements were processed to obtain the dynamic forces at the blade passing frequency, also over a wide range of flow rates. Afterwards, these results were used to check the predictions from the numerical simulations. For some flow rates, the bigger diameter produced higher radial forces, but this was not to be a general rule for all the operating points. This paper describes the work carried out and summarizes the experimental and the numerical results, for both radial gaps. The steady and unsteady forces at the blade passing frequency were calculated by radial integration of the pressure distributions on the shroud side of the pump volute. For the unsteady forces, the numerical model allowed a separate analysis of the terms due to the pressure pulsations and terms related to the momentum exchange in the impeller. In this way, the whole operating range of the pump was studied and analyzed to account for the static and dynamic flow effects. The unsteady forces are very important when designing the pump shaft as they can produce a fatigue collapse if they are not kept under a proper working value.

Improvement of Centrifugal Pump Performance by Using Different Impeller Diffuser Angles with and Without Vanes

2018 ◽  
Vol 35 (4) ◽  
pp. 577-589 ◽  
Author(s):  
D. Khoeini ◽  
E. Shirani ◽  
M. Joghataei
Keyword(s):  
Centrifugal Pump ◽  
Experimental Studies ◽  
High Flow ◽  
Divergence Angle ◽  
Centrifugal Pumps ◽  
Pump Impeller ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Operating Region ◽  
Overall Efficiency

ABSTRACTThis study aims at improving the performance of a centrifugal pump by using different angular diffusers on the downstream side of the centrifugal pump impeller. Numerical and experimental studies have been carried out on different vaned and non-vaned diffuser with three different wall divergence angle (α) of 0°, 5° and 10° to achieve that purpose. The data analyses show good agreement between the numerical and experimental results. They reveal profound effect of the divergence angle (α) of angular vaned diffuser on the head and overall efficiency of centrifugal pumps especially at high flow rates as they broaden operating region of the centrifugal pump. In fact it is found that the head and overall efficiency of impeller with vaned diffuser α = 10° enhance by 15.4 and 9 percent respectively compared to that of centrifugal pump with no vaned diffuser at high flow rates. Furthermore the head and overall efficiency of impeller with vaned diffuser α = 10° increase by 5.7 and 7 percent respectively in comparison with the impeller with vaned diffuser α = 0°.

scholarly journals Simulation of Flow in Turbopump Vaneless and Vaned Diffusers with Fluid Injection

2000 ◽  
Vol 6 (1) ◽  
pp. 57-65
Author(s):  
Ali Ogut ◽  
Diego Garcia Pastor
Keyword(s):  
Flow Separation ◽  
Flow Region ◽  
Design Flow ◽  
Low Flow ◽  
Fluid Injection ◽  
Bottom Surface ◽  
Suction Surface ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Wide Range

In future space missions by NASA there will be a need for “Space Transfer Vehicles” to perform varying orbital transfers and descents. This requires engines capable of producing different levels of thrust. To accomplish this, the turbopumps employed in these engines should efficiently provide a wide range of flow outputs. However, current fuel and oxidizer turbopumps with vaned diffusers do not perform efficiently at off-design (low) flow rates mainly due to flow separation in the vaned diffuser.This paper evaluates the effectiveness of boundary layer control by fluid injection (blowing) for suppressing or eliminating the flow separation in a vaned diffuser. A 3-D flow model including vaneless and vaned diffusers of a liquid hydrogen (LH2) turbopump is studied using the CFD code FIDAP. The paper presents the results of the model at design and offdesign flow conditions.The model results showed that flow separation occurs at the top or suction surface of the vaneless diffuser and at the bottom or pressure surface of the vaned diffuser at off-design flow rates. When fluid injection was applied through the bottom surface of the vaned diffuser, the separated flow region was reduced almost entirely, resulting in an increase in pressure recovery of up to 21% with varying fluid injection rates. Results also showed that there is an optimum injection rate which is most effective in reducing or eliminating the region of flow separation.

scholarly journals Experimental Study of The Influence of Fluid Flow Rate on The Risk of Rock Destruction

2021 ◽  
Author(s):  
Sudad H Al-Obaidi
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Design Flow ◽  
Fluid Flow Rate ◽  
Reservoir Properties ◽  
Rock Destruction ◽  
Flow Rates ◽  
Wide Range ◽  
Deformation Properties ◽  
Gas Fields

The stresses acting in the vicinity of wells have a significant impact on the flow properties of the reservoir and, as a result, on the flow rate of oil wells. The magnitude of such stresses depends on the deformation properties of the rock and on the oil pressure at the bottom of the well. In this work, an attempt to study the effect of flow fields (formation flow rate, well flow rates) on rocks in near-wellbore zones was performed. For this purpose, the correlation of such indicators as the fluid flow rate and the risk of destruction of the rocks of the productive deposits of one of the gas fields were experimentally studied. The experiments were performed on chosen core samples with quite wide range of flow and volumetric reservoir properties. It was concluded that the rock samples of the productive deposits of the studied formation do not collapse under the influence of pressure gradients corresponding to the design flow rates.

Numerical and Experimental Analysis of Flow Phenomena in a Centrifugal Pump Operating Under Low Flow Rates

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Yanxia Fu ◽  
Jianping Yuan ◽  
Shouqi Yuan ◽  
Giovanni Pace ◽  
Luca d'Agostino ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Internal Flow ◽  
Flow Coefficient ◽  
Flow Instabilities ◽  
Low Flow ◽  
Flow Rates ◽  
Wide Range

The characteristics of flow instabilities as well as the cavitation phenomenon in a centrifugal pump operating at low flow rates were studied by experimental and numerical means, respectively. Specially, a three-dimensional (3D) numerical model of cavitation was applied to simulate the internal flow through the pump and suitably long portions of the inlet and outlet ducts. As expected, cavitation proved to occur over a wide range of low flow rates, producing a characteristic creeping shape of the head-drop curve and developing in the form of nonaxisymmetric cavities. As expected, the occurrence of these cavities, attached to the blade suction sides, was found to depend on the pump's flow coefficient and cavitation number. The experiments focused on the flow visualization of the internal flow patterns by means of high-speed digital movies and in the analysis of the inlet pressure pulsations near the impeller eye by means of fast response pressure transducers. The experimental results showed that the unsteady behavior of the internal flow in the centrifugal pump operating at low flow rates has the characteristics of a peculiar low-frequency oscillation. Meanwhile, under certain conditions, the low-frequency pressure fluctuations were closely correlated to the flow instabilities induced by the occurrence of cavitation phenomena at low flow rates. Finally, the hydraulic performances of the centrifugal pump predicted by numerical simulations were in good agreement with the corresponding experimental data.

scholarly journals Experimental Investigation of the Stalled Flow in a Centrifugal Pump-Turbine With Varied Diffuser

1990 ◽  
Author(s):  
Marina Ubaldi ◽  
Pietro Zunino
Keyword(s):  
Centrifugal Pump ◽  
Total Pressure ◽  
Fourier Transforms ◽  
Instantaneous Velocity ◽  
Low Flow ◽  
Pump Turbine ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Flow Rates ◽  
Pump Operation

Detailed measurements have been made of the stalled flow in a centrifugal pump-turbine model operating in air. Instantaneous velocity, total pressure and flow angle have been measured with hot wire and pressure probes at the impeller inlet and outlet and in the vaned diffuser for several pump operating points, ranging from nominal to very low flow rates. Three distinct stall phenomena have been found to affect the pump operation at reduced flow rates. The unsteady characteristics of these unstable flows have been analysed both in time and in frequency domain by means of Fourier transforms of the velocity signals. The changes in the flow structure, correlated to the occurrence of the observed stall conditions, have been investigated by means of phase-locked ensemble averages of the instantaneous velocity components at the impeller outlet and surveys of the mean total pressure and absolute flow angle distributions within the diffuser passages.

scholarly journals Experimental Investigation of Vibration Characteristics in a Centrifugal Pump with Vaned Diffuser

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Kai Wang ◽  
Xin Lu ◽  
Xianghui He
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Energy Performance ◽  
Vibration Characteristics ◽  
Maximum Efficiency ◽  
Monitoring Point ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Vibration Intensity ◽  
Specific Speed

In order to investigate the vibration characteristics of centrifugal pump, a centrifugal pump with vaned diffuser whose specific speed is 190 was chosen for this research. Both the experiments of energy performance and vibration characteristics of the pump were performed. The results indicate that when flow rate of the pump is 270 m3/h, the head is 15.03 m and the efficiency is 71.47%. The maximum efficiency is 71.71% when the flow rate of the pump is 233 m3/h and the head is 16.92 m. And a wide frequency band of vibration appears at 600 Hz at outlet flange of the pump. The vibration intensity at the outlet flange is largest. The vibration intensities at both sides of bearing casing are slighter than those at outlet flange and larger than those at motor base. The vibration intensity at the motor base is larger than that at pump base, and the vibration intensity at the pump body is the lowest. The vibration intensity of monitoring point M4 in the X direction under 0.8Qd is 1.27 mm/s, which is the maximum under three flow rates.

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