Numerical Analysis of Centrifugal Pumps Running in Turbine Mode Under Dynamic Operating Conditions

2017 ◽  
Author(s):  
Vincenzo De Rose ◽  
Francesca Martelli ◽  
Massimo Milani ◽  
Luca Montorsi
Keyword(s):  
Cfd Simulation ◽  
Energy Conversion Efficiency ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Pump Operation ◽  
Electric Generator ◽  
Reverse Mode ◽  
Hydropower Plants ◽  
Dynamic Operating ◽  
Turbine Mode

The use of pumps as turbines (PAT) has gained importance in the recent years as a possible alternative to specifically developed turbine for mini/micro hydropower plants. The use of production pump for hydropower generation reduces the capital cost of the plant but the energy conversion efficiency can be remarkably lower. The paper analyses the performance of a production centrifugal pump running both in direct and reverse mode. The analysis calculates theoretically the behavior of the PAT under the best efficiency point and extends the investigation to other operating points using both a combined theoretical approach and CFD simulation under dynamic conditions. The effects of possible modifications to the initial design of the pump are investigated when running in turbine mode and their influence on the standard pump operation is also determined. Numerical simulation demonstrates that the impeller trimming leads to improvement in the PAT efficiency in some operating conditions. Conversely, the rotational speeds close to the values typical for the electric generator reduce the PAT performance. Finally, the modification of the impeller geometry at the turbine inlet increases the PAT efficiency but lowers the performance of the machine when running in pump mode.

scholarly journals Characteristics of Centrifugal Pumps Working in Direct or Reverse Mode: Focus on the Unsteady Radial Thrust

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Anthony Couzinet ◽  
Laurent Gros ◽  
Daniel Pierrat
Keyword(s):  
Numerical Data ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Specific Test ◽  
Pump Operation ◽  
Reverse Mode ◽  
Ansys Cfx ◽  
Test Loop ◽  
Radial Forces ◽  
Radial Thrust

Experimental and numerical investigations have been carried out to study the behaviour of a centrifugal pump operating in direct mode or turbine mode. First of all, the complete characteristics (head, power, and efficiency) were measured experimentally using a specific test loop. The numerical data obtained from a CFD study performed with the ANSYS CFX software and based on steady state and unsteady approaches were compared to the experimental results. The representation in the 4 operating quadrants shows the various operating zones where the head is always positive. Then, the unsteady radial forces were analysed from transient computations. The results obtained for the pump operation are consistent with the literature and extended to the nonnormal operating conditions, namely, for very high flowrate values. The evolution of the radial load during turbine operation is presented for various partial flow operating points.

scholarly journals Improving the Energy Conversion Efficiency for Hydrokinetic Turbines Using MPPT Controller

2020 ◽  
Vol 10 (21) ◽  
pp. 7560
Author(s):  
Rareș-Andrei Chihaia ◽  
Ionuț Vasile ◽  
Gabriela Cîrciumaru ◽  
Sergiu Nicolaie ◽  
Emil Tudor ◽  
...  
Keyword(s):  
Control System ◽  
Energy Conversion Efficiency ◽  
Buck Converter ◽  
Operating Conditions ◽  
Maximum Point ◽  
Electric Generator ◽  
Point Tracking ◽  
Hydrokinetic Turbine ◽  
The Individual ◽  
Power Curves

The research presented in this paper involves the design of a power control system for a hydrokinetic turbine previously tested in real operating conditions. A maximum power point tracking (MPPT) algorithm was designed and simulated using the required parameters for a specific electric generator. The proposed system consists of a generator connected to the hydrokinetic turbine, a three-phase uncontrolled rectifier, a direct current (DC) boost converter with MPPT control to extract maximum available power, and a buck converter to control the amount of power delivered to the load. In order to test the MPPT algorithm, we built the individual blocks on the basis of the corresponding equations of each component. The algorithm considered the specific parameters of the previously tested turbine as input data and simulated the same water velocities for which the turbine had been tested. Thus, the simulation predicted a power output of 105 W for a water velocity of 1.33 m/s, 60 W for 1 m/s, and 30 W for 0.83 m/s. The efficiency of the control system was demonstrated when the instantaneous power value was maintained at a maximum point, regardless of the rotational speed according to the experimental power curves of the driving rotor obtained for certain water velocities.

Numerical Simulation of Inner Flow in a Double Blades Pump Based on OpenFOAM and its PIV Verification

2012 ◽  
Author(s):  
Yun Ren ◽  
Houlin Liu ◽  
Kai Wang ◽  
Minggao Tan ◽  
Denghao Wu ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Flow Behavior ◽  
Energy Performance ◽  
Operating Conditions ◽  
Centrifugal Pumps ◽  
Complex Flow ◽  
Unstable Flow ◽  
Software Packages ◽  
Flow Phenomena ◽  
Particle Imaging

The presence of unstable flow phenomena may significantly alter the flow pattern and characteristics of centrifugal pumps; that is, the unstable flows may seriously deteriorate the pumps performance. In this paper, considering the high cost of running license fees and not available with all the computing resources, a high quality Open Source CFD simulation platform like OpenFOAM instead of commercial software packages is adopted. Furthermore, the required capability such as GGI is added and boundary conditions are specialized to better simulate complex flow behavior through rotor-stator components in a double blades pump, whose specific speed is 115.6. In order to disclose the characteristics completely, six research schemes are developed and are now presented in this paper. The ratios (Q/Qd) of the flow rate are 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, respectively. The task mainly focuses on the comparison of energy performance under different operating conditions between numerical calculations and experiments, the analysis of the inner flow in the impeller and the comparison of the velocity field in the impeller mid-height between simulation data and the Particle Imaging Velocimetry (PIV) experimental data. The results show that good agreements are found both in terms of the energy performance with experimental results and computed velocities with the PIV data, but improvements can be made.

scholarly journals CFD Analysis on Pumps Working as Turbines

1970 ◽  
Vol 6 ◽  
pp. 35-37 ◽  
Author(s):  
Himanshu Nautiyal ◽  
Varun Kumar ◽  
Anoop Thakur
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Design Tool ◽  
Recent Attempt ◽  
Cfd Analysis ◽  
Centrifugal Pumps ◽  
Small Hydropower ◽  
Hydropower Plants ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Mode

 Reverse running centrifugal pumps are  an effective source of reducing the equipment cost in small hydropower plants. The manufacturers do not provide any information on the performance and fow characteristics when pumps are operated in turbine mode. Lack of Pump as Turbine (PAT) performance data is a signifcant barrier to the wider use of PAT. Application of Computational Fluid Dynamics (CFD) is a recent attempt for predicting the performance of PAT. CFD analysis is an effective design tool for predicting the performance of reverse running operation of centrifugal pumps. But some deviationsstill exist in experimental and CFD results of reverse operation of pumps. Future works in the feld of computational analysis can further improve the prediction of pumps in reverse operation. Key words:  Pump as Turbine (PAT); Computational Fluid Dynamics (CFD); PumpDOI: 10.3126/hn.v6i0.4191   Hydro Nepal Vol 6, January 2010 Page : 35-37 Uploaded Date:24 January, 2011

scholarly journals Turbine Mode Performance Evaluation of Centrifugal Pump

2019 ◽  
Vol 9 (1) ◽  
pp. 6804-6809
Keyword(s):  
Performance Evaluation ◽  
Centrifugal Pump ◽  
Cfd Simulation ◽  
Simulation Software ◽  
Centrifugal Pumps ◽  
Pump Mode ◽  
Mode Operation ◽  
Performance Curves ◽  
The Difference ◽  
Turbine Mode

This paper presents the performance evaluation results of a radial discharge centrifugal pump obtained through experimentation and CFD simulation. The paper also presents a brief theory behind the difference in the performance of a centrifugal pump operated in pump mode and turbine mode. The pump CFD simulation is performed with Star CCM+ simulation software. The pumps studied are both mono block radial discharge centrifugal pumps with rated speed of rotation per minute as 1400 and 2800 and specific speeds 20.65 (m,m3 /s) and 35.89 (m,m3 /s) respectively. The CFD results were first validated for pump mode by comparing them with the manufacturer provided performance curves. The results of CFD simulation for turbine mode operation are then compared with experimentally obtained results. The paper also presents a brief theory about PAT concept.

Experimental Approach to Predict the Residual Axial Thrust in Centrifugal Pumps

2019 ◽  
Author(s):  
Giulio Elicio ◽  
Francesco Annese
Keyword(s):  
Pressure Distribution ◽  
Rotational Speed ◽  
Experimental Approach ◽  
Thrust Bearing ◽  
High Energy ◽  
Operating Conditions ◽  
Back Side ◽  
Centrifugal Pumps ◽  
Axial Thrust ◽  
Pump Operation

Abstract The residual axial thrust of a centrifugal pump is the vector resultant of the hydraulic components of impellers and sleeves, the momentum force and other imbalance forces and is bear by the thrust bearing. Among all the components, the hydraulic is by far the most important because it is typically one order of magnitude bigger than the others and the final residual axial thrust itself; but it is also the most difficult to calculate or estimate. This is mainly due a lot of uncertainties in the definition of the pressure distribution in the sidewall gap, dependent on the rotational speed, the leakages through the annular seals, the inlet swirl to the sidewall, the axial alignment of the impeller with the stator, the geometric tolerances and the pump operation. In this paper an experimental approach to validate and calibrate the formulation to predict the hydraulic component of the impellers is presented. The typical formulation to evaluate the parabolic behavior of the pressure distribution is based on a series of coefficients, coming from literature, to consider all the above-mentioned influences. This formulation can be considered satisfying when dealing with pumps with back-to-back arrangement of the impellers on the rotor, since the hydraulic components are almost balanced. But with in-line configuration, all the hydraulic components of the impellers act against one direction and most of their force can be balanced by means of a balance drum, much more reliable than a balance disk. An experimental test campaign on a high energy diffuser pump was performed. The pump was equipped with load cells and temperature probes on the thrust bearing, and a special balancing line with a regulating bleed-off valve whose aim was to partialize the flowrate routed from the back side of the balancing drum to the suction. By throttling the bleed-off valve, it was possible to measure the hydraulic components of the impellers in very different operating conditions of the balancing drum, at different rotational speed and at different flowrates included zero residual axial thrust capability. As results of this campaign, once calibrated the coefficients on the full-scale pump, it is possible to calculate the residual axial thrust based on specific pressure measurements of the model test of a stage hydraulic; this also allows a thorough optimization of the thrust bearing selection.

Performance Improvements in Cooker-Top Gas Burners for Small Aspect Ratio Changes

2017 ◽  
Vol 9 (4) ◽  
Author(s):  
Robson L. Silva ◽  
Bruno V. Sant′Ana ◽  
José R. Patelli ◽  
Marcelo M. Vieira
Keyword(s):  
Energy Conversion ◽  
Fuel Consumption ◽  
Conversion Efficiency ◽  
Minimum Energy ◽  
Energy Conversion Efficiency ◽  
Energy Performance ◽  
Operating Conditions ◽  
Lower Fuel Consumption ◽  
Performance Improvements ◽  
Aspect Ratios

This paper aims to identify performance improvements in cooker-top gas burners for changes in its original geometry, with aspect ratios (ARs) ranging from 0.25 to 0.56 and from 0.28 to 0.64. It operates on liquefied petroleum gas (LPG) and five thermal power (TP) levels. Considering the large number of cooker-top burners currently being used, even slight improvements in thermal performance resulting from a better design and recommended operating condition will lead to a significant reduction of energy consumption and costs. Appropriate instrumentation was used to carry out the measurements and methodology applied was based on regulations from INMETRO (CONPET program for energy conversion efficiency in cook top and kilns), ABNT (Brazilian Technical Standards Normative) and ANP—National Agency of Petroleum, Natural Gas (NG) and Biofuels. The results allow subsidizing recommendations to minimum energy performance standards (MEPS) for residential use, providing also higher energy conversion efficiency and/or lower fuel consumption. Main conclusions are: (i) Smaller aspect ratios result in the same heating capacity and higher efficiency; (ii) higher aspect ratios (original burners) are fuel consuming and inefficient; (iii) operating conditions set on intermediate are lower fuel consumption without significant differences in temperature increases; (iv) Reynolds number lower than 500 provides higher efficiencies.

scholarly journals Binary Amplitude Reflection Gratings for X-ray Shearing and Hartmann Wavefront Sensors

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 536
Author(s):  
Kenneth A. Goldberg ◽  
Antoine Wojdyla ◽  
Diane Bryant
Keyword(s):  
Operating Conditions ◽  
Design Parameters ◽  
Wavefront Aberration ◽  
Light Sources ◽  
Wavefront Sensors ◽  
X Ray ◽  
New Class ◽  
Coherent Wave ◽  
Reflection Gratings ◽  
Dynamic Operating

New, high-coherent-flux X-ray beamlines at synchrotron and free-electron laser light sources rely on wavefront sensors to achieve and maintain optimal alignment under dynamic operating conditions. This includes feedback to adaptive X-ray optics. We describe the design and modeling of a new class of binary-amplitude reflective gratings for shearing interferometry and Hartmann wavefront sensing. Compact arrays of deeply etched gratings illuminated at glancing incidence can withstand higher power densities than transmission membranes and can be designed to operate across a broad range of photon energies with a fixed grating-to-detector distance. Coherent wave-propagation is used to study the energy bandwidth of individual elements in an array and to set the design parameters. We observe that shearing operates well over a ±10% bandwidth, while Hartmann can be extended to ±30% or more, in our configuration. We apply this methodology to the design of a wavefront sensor for a soft X-ray beamline operating from 230 eV to 1400 eV and model shearing and Hartmann tests in the presence of varying wavefront aberration types and magnitudes.

CFD Simulation of a Co-rotating Twin-screw Extruder: Validation of a Rheological Model for a Starch-Based Dough for Snack Food

2017 ◽  
Vol 14 (2) ◽  
Author(s):  
Giorgia Tagliavini ◽  
Federico Solari ◽  
Roberto Montanari
Keyword(s):  
Cfd Simulation ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Second Phase ◽  
Snack Food ◽  
Suitable Model ◽  
Twin Screw Extruder ◽  
Parallel Plates ◽  
Screw Extruder ◽  
Twin Screw

AbstractThe extrusion of starch-based products has been a matter of interest, especially for the pasta and the snack food production. In recent years, twin-screw extruders for snack food have been studied from both structural and fluid dynamics viewpoints. This project started from the rheological characterization of a starch-based dough (corn 34 wt%, tapioca 32 wt%), comparing viscosity values acquired in laboratory with different theoretical models found in literature. A computational fluid dynamic (CFD) simulation recreating the simple case of a fluid flow between two parallel plates was carried out to validate the former comparison. After the rheological validation was completed, the second phase of this work covered a 3D CFD simulation of the first part of the twin-screw extruder (feeding zone). The objective was to find a suitable model for describing the dough rheological behavior and the operating conditions of a co-rotating intermeshing twin-screw extruder. Once the model would be defined, it would allow to investigate several working conditions and different screws geometries of the machine, predicting the evolution of the product rheological properties.

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