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Stan Shiels - One of the best experts on this subject based on the ideXlab platform.

  • Chapter 7 – The importance of running clearances in Centrifugal Pumps
    Stan Shiels on Centrifugal Pumps, 2004
    Co-Authors: Stan Shiels
    Abstract:

    Publisher Summary Running clearance in Centrifugal Pumps is done to achieve acceptable pump efficiency. This chapter presents the case of a single-stage overhung pump with a semi-open impeller, which has back pump-out vanes; a single-stage overhung pump with a fully enclosed impeller with shrouds back and front of the vanes; and a single-stage overhung pump of either semi-open or fully enclosed impeller design. The areas affected include hydraulic performance, energy consumption, reliability, and maintenance costs. These areas reflect the more common effects of running clearances in conventional designs of Centrifugal Pumps. Specific applications involving high energy or high speed Centrifugal Pumps often require even closer adherence to recommended tolerances. Materials with galling tendencies often require greater running clearances, as even a minor rub can cause a major failure with such materials. Further, optimized Centrifugal pump application demands close attention to pump internal running clearances as one of the key elements in an excellent maintenance program.

  • Chapter 26 – Troubleshooting Centrifugal Pumps: Rolling element bearing failures
    Stan Shiels on Centrifugal Pumps, 2004
    Co-Authors: Stan Shiels
    Abstract:

    Publisher Summary This chapter addresses the key areas of Centrifugal pump mechanical failure diagnosis. The causes of bearing failure in Centrifugal Pumps are often related to areas of hydraulics or maintenance, which is also included in the analysis, along with the common areas such as lubrication, maintenance, and design. There are five prime causes of rolling element bearing failure—excessive load, improper lubrication, contamination of the lubricant, poor maintenance practices, and incorrect specification. Focusing on the five key areas affecting rolling element bearing life in Centrifugal Pumps allows considering and including or eliminating areas of concern. It also avoids much of the trial and error often associated with troubleshooting. One can also make some very logical and solid deductions, which helps to address the area really associated with the failure.

  • Troubleshooting Centrifugal Pumps: rolling element bearing failures
    World Pumps, 2001
    Co-Authors: Stan Shiels
    Abstract:

    Abstract Diagnosing the cause of bearing failures in Centrifugal Pumps requires knowledge of bearings and their lubrication and knowledge of pump design and operating characteristics. Stan Shiels argues it also often involves knowledge of the pump's operating envelope (the range of flow rates, which it is asked to provide, and the duration of these flow rates). Familiarity with good bearing maintenance practices is also important.

  • The importance of running clearances in Centrifugal Pumps
    World Pumps, 1997
    Co-Authors: Stan Shiels
    Abstract:

    Abstract All Centrifugal Pumps must have clearance between the stationary pump casing and the rotating element. In single stage Pumps this clearance is limited to the clearance between the impeller surfaces and the casing, and the clearance between the seal cavity (or stuffing-box) throat bushing and the shaft. There are a number of close tolerance clearances which, if altered, will change one or more of a pump's characteristics.

Joao Nuno Gomes Borga Delgado - One of the best experts on this subject based on the ideXlab platform.

  • variable speed operation of Centrifugal Pumps running as turbines experimental investigation
    Renewable Energy, 2019
    Co-Authors: Joao Nuno Gomes Borga Delgado, Joao Paulo B C C Ferreira, Didia Covas, Francois Avellan
    Abstract:

    Abstract Pumps running as turbines are pointed out as a cost-effective solution for energy recovery in pressurised water supply systems. However, these hydraulic machines feature low efficiency under variable discharge operation due to the lack of an inlet flow control component. Variable speed operation is an approach for controlling the discharge at the pump as turbine inlet aiming at increasing the operational efficiency. This research work presents the experimental investigation for measuring the variable speed characteristic curves of Pumps running as turbines, focusing on the turbine and on the extended operation modes. Three single-stage end-suction closed-impeller Centrifugal Pumps with different unit specific speed values are tested. Turbine mode test results show that the discharge-specific energy operating range is broadened with increasing efficiency if the machines are operated with variable speed. Extended operation results show that these hydraulic machines do not feature the instability region near the runaway conditions, the so-called the “s-curve”. Outcomes of this experimental investigation provide the required insights for establishing the design technical specifications of micro hydropower plants with variable speed Pumps running as turbines, aiming at maximizing the energy recovered in pressurised water supply systems.

Ahmad Nourbakhsh - One of the best experts on this subject based on the ideXlab platform.

  • Experimental evaluation of temperature rise in Centrifugal Pumps at partial flow rates
    Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2018
    Co-Authors: Atta Sojoudi, Ahmad Nourbakhsh, Hossein Shokouhmand
    Abstract:

    When the Centrifugal Pumps operate near shut-off condition, different kinds of energy losses happen from inlet to discharge nozzle leading to lower hydraulic performance and overall efficiency. A part of dissipated energy turns into heat and increases the operating liquid temperature. This may seem to be very dangerous when talking about pumping oil or any other flammable chemical liquids. In the present investigation, several Centrifugal Pumps were selected to perform experimental analysis of measuring temperature rise at inlet and discharge nozzles during part load operation. Pumps were entirely insulated using glass wool to prevent heat leakage from pump casing to the environment and pure water was selected to play as the working fluid. Temperature rise of Pumps was reported from start time up to assuaging steady-state condition. Obtained results demonstrated that higher rotational speed of impeller led to higher value of outlet water temperature in a shorter time rather than lower rotational speeds. Steady-state temperature values were used to establish a novel relation for temperature rise that can be implemented for wide range of Centrifugal Pumps.

  • the comparison of multi objective particle swarm optimization and nsga ii algorithm applications in Centrifugal Pumps
    Engineering Optimization, 2011
    Co-Authors: Ahmad Nourbakhsh, Hamed Safikhani, Shahram Derakhshan
    Abstract:

    In the present study, multi-objective optimization of Centrifugal Pumps is performed in three steps. In the first step, efficiency (η) and the required net positive suction head (NPSHr) in a set of Centrifugal Pumps are numerically investigated using commercial software. Two meta-models based on the evolved group method of data handling (GMDH) type neural networks are obtained in the second step for modeling of η and NPSHr with respect to geometrical design variables. Finally, using the obtained polynomial neural networks, a multi-objective particle swarm optimization method (MOPSO) is used for Pareto-based optimization of Centrifugal Pumps considering two conflicting objectives, η and NPSHr. The Pareto results of the MOPSO method are also compared with those of a multi-objective genetic algorithm (NSGA II). It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of Centrifugal Pumps can be discovered by Pareto-based multi-objective opt...

  • experimental study of characteristic curves of Centrifugal Pumps working as turbines in different specific speeds
    Experimental Thermal and Fluid Science, 2008
    Co-Authors: Shahram Derakhshan, Ahmad Nourbakhsh
    Abstract:

    Pump manufacturers do not normally provide the characteristic curves of their Pumps working as turbines. Therefore, establishing a correlation between the performances of direct (pump) and reverse (turbine) modes is essential in selecting the proper machine. In this paper, several Centrifugal Pumps (N{sub s} < 60 (m, m{sup 3}/s)) were tested as turbines. Using experimental data, some relations were derived to predict the best efficiency point of a pump working as a turbine, based on pump hydraulic characteristics. Validity of the presented method was shown using some referenced experimental data. Two equations were presented to estimate the complete characteristic curves of Centrifugal Pumps as turbines based on their best efficiency point. Deviations of suggested method from experimental data were considered and discussed. Finally, a procedure was presented for selecting a suitable pump to work as a turbine in a small hydro-site. (author)

Francois Avellan - One of the best experts on this subject based on the ideXlab platform.

  • variable speed operation of Centrifugal Pumps running as turbines experimental investigation
    Renewable Energy, 2019
    Co-Authors: Joao Nuno Gomes Borga Delgado, Joao Paulo B C C Ferreira, Didia Covas, Francois Avellan
    Abstract:

    Abstract Pumps running as turbines are pointed out as a cost-effective solution for energy recovery in pressurised water supply systems. However, these hydraulic machines feature low efficiency under variable discharge operation due to the lack of an inlet flow control component. Variable speed operation is an approach for controlling the discharge at the pump as turbine inlet aiming at increasing the operational efficiency. This research work presents the experimental investigation for measuring the variable speed characteristic curves of Pumps running as turbines, focusing on the turbine and on the extended operation modes. Three single-stage end-suction closed-impeller Centrifugal Pumps with different unit specific speed values are tested. Turbine mode test results show that the discharge-specific energy operating range is broadened with increasing efficiency if the machines are operated with variable speed. Extended operation results show that these hydraulic machines do not feature the instability region near the runaway conditions, the so-called the “s-curve”. Outcomes of this experimental investigation provide the required insights for establishing the design technical specifications of micro hydropower plants with variable speed Pumps running as turbines, aiming at maximizing the energy recovered in pressurised water supply systems.

Shouqi Yuan - One of the best experts on this subject based on the ideXlab platform.

  • Numerical and experimental study on flow-induced noise at blade-passing frequency in Centrifugal Pumps
    Chinese Journal of Mechanical Engineering, 2014
    Co-Authors: Yang Jun, Shouqi Yuan, Jianping Yuan, Ji Pei
    Abstract:

    With the increasing noise pollution, low noise optimization of Centrifugal pimps has become a hot topic. However, experimental study on this problem is unacceptable for industrial applications due to unsustainable cost. A hybrid method that couples computational fluid dynamics (CFD) with computational aeroacoustic software is used to predict the flow-induced noise of Pumps in order to minimize the noise of Centrifugal Pumps in actual projects. Under Langthjem’s assumption that the blade surface pressure is the main flow-induced acoustic source in Centrifugal Pumps, the blade surface pressure pulsation is considered in terms of the acoustical sources and simulated using CFX software. The pressure pulsation and noise distribution in the near-cutoff region are examined for the blade-passing frequency (BPF) noise, and the sound pressure level (SPL) reached peaks near the cutoff that corresponded with the pressure pulsation in this region. An experiment is performed to validate this prediction. Four hydrophones are fixed to the inlet and outlet ports of the test pump to measure the flow-induced noise from the four-port model. The simulation results for the noise are analyzed and compared with the experimental results. The variation in the calculated noise with changes in the flow agreed well with the experimental results. When the flow rate was increased, the SPL first decreased and reached the minimum near the best efficient point (BEP); it then increased when the flow rate was further increased. The numerical and experimental results confirmed that the BPF noise generated by a blade-rotating dipole roughly reflects the acoustic features of Centrifugal Pumps. The noise simulation method in current study has a good feasibility and suitability, which could be adopted in engineering design to predict and optimize the hydroacoustic behavior of Centrifugal Pumps.

  • assessment of a turbulence model for numerical predictions of sheet cavitating flows in Centrifugal Pumps
    Journal of Mechanical Science and Technology, 2013
    Co-Authors: Houlin Liu, Shouqi Yuan, Yong Wang, Dongxi Liu, Jian Wang
    Abstract:

    Various approaches have been developed for numerical predictions of unsteady cavitating turbulent flows. To verify the influence of a turbulence model on the simulation of unsteady attached sheet-cavitating flows in Centrifugal Pumps, two modified RNG k-ɛ models (DCM and FBM) are implemented in ANSYS-CFX 13.0 by second development technology, so as to compare three widespread turbulence models in the same platform. The simulation has been executed and compared to experimental results for three different flow coefficients. For four operating conditions, qualitative comparisons are carried out between experimental and numerical cavitation patterns, which are visualized by a high-speed camera and depicted as isosurfaces of vapor volume fraction α v = 0.1, respectively. The comparison results indicate that, for the development of the sheet attached cavities on the suction side of the impeller blades, the numerical results with different turbulence models are very close to each other and overestimate the experiment ones slightly. However, compared to the cavitation performance experimental curves, the numerical results have obvious difference: the prediction precision with the FBM is higher than the other two turbulence models. In addition, the loading distributions around the blade section at midspan are analyzed in detail. The research results suggest that, for numerical prediction of cavitating flows in Centrifugal Pumps, the turbulence model has little influence on the development of cavitation bubbles, but the advanced turbulence model can significantly improve the prediction precision of head coefficients and critical cavitation numbers.

  • investigation on flow induced noise due to backflow in low specific speed Centrifugal Pumps
    Advances in Mechanical Engineering, 2013
    Co-Authors: Shouqi Yuan, Jianping Yuan, Yun Liang
    Abstract:

    Flow-induced noise causes disturbances during the operation of Centrifugal Pumps and also affects their performance. The Pumps often work at off-design conditions, mainly at part-load conditions, b...

  • experimental investigation on the flow induced noise under variable conditions for Centrifugal Pumps
    Chinese Journal of Mechanical Engineering, 2012
    Co-Authors: Shouqi Yuan, Jianping Yuan, Jun Yang, Yin Luo, Ji Pei
    Abstract:

    With extensively using of Centrifugal Pumps, noise generation in these Pumps is increasingly receiving research attention in recent years. The noise sources in Centrifugal Pumps are mainly composed of mechanical noise and flow-induced noise. And the study of flow-induced noise has become a hotspot and important domain in the field. The flow-induced noise closely related to the inner pressure pulses and vibration of volute in Pumps, therefore, it is necessary to research the interaction and mechanism among them. To investigate the relationships, a test system is designed which includes a test loop and a measurement system. The hydrophones and pressure sensors are installed on the outlet of the pump and vibration acceleration sensors are disposed on the pump body. Via these instruments, the signals of noise, pressure pulses and vibration are collected and analyzed. The results show that the level of flow-induced noise becomes smaller as the flow increment during low flow rate operations, and it is steadily close to the design point, then it increases with the growing of flow rate in high flow rate conditions. Furthermore, there are some similar peak points in the power spectrum charts of noise, pressure pulses and vibration. The broadband noise at low flow rate is mostly focused on the region of 0–40 times shaft frequency, which is mostly made by rotating stall and vortex; while the noise at high flow rate conditions is focused on the region of 60–100 times shaft frequency, which may be mostly made by cavitations. The proposed research is of practical and academic significance to the study of noise reduction for Centrifugal Pumps.

  • Applicability of Turbulence Models on Characteristics Prediction of Centrifugal Pumps
    ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1 Symposia – Parts A B C and D, 2011
    Co-Authors: Yong Wang, Shouqi Yuan, Houlin Liu, Minggao Tan, Minhua Shu
    Abstract:

    In order to research the applicability of turbulence model on characteristics prediction of Centrifugal Pumps at the design condition, standard k-e turbulence model, k-ω turbulence model and SST turbulence model are selected, which are commonly used in the numerical prediction for head, efficiency and NPSHr of the Centrifugal Pumps. By using commercial code ANSYS CFX, the all three turbulent models are used to predict the characteristics of six Centrifugal Pumps with the different specific speeds at the design condition, which are varied from 34.3 to 260.5. The calculation results are compared with the experimental data, and the comparison indicates that all the prediction results obtained from different turbulence models are more or less different from the experimental data. The head and efficiency predicted by SST turbulence model and k-ω turbulence model are closer and they are all bigger than that predicted by k-e turbulence model. For low specific speed Centrifugal Pumps, the head and efficiency predicted by SST model and the NPSHr predicted by k-e turbulence model are more closer to the experimental values; while for the medium and high specific speed Centrifugal Pumps, the head and efficiency predicted by k-e turbulence model are better than that predicted by other models. The k-ω turbulence model and k-e turbulence model are the best choice to predict NPSHr of medium and high specific speed Centrifugal Pumps respectively.© 2011 ASME