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Experimental Investigation of Centrifugal Pump Working as Turbine for Small Hydropower Systems  [cached]
Himanshu Nautiyal,Varun Varun,Anoop Kumar,Sanjay Yadav Sanjay Yadav
Energy Science and Technology , 2011,
Abstract: An experimental investigation of centrifugal pump has been carried out to study its characteristics in pump and turbine mode operation. By using the experimental results of tested pump and pumps of some previous researchers, new correlations have been developed by using its best efficiency and specific speed in pump mode. Values obtained from the derived correlations show good match with experimental results. These correlations would be very helpful for the performance prediction of pump working as turbine. Key words: PAT; Centrifugal pump; Specific speed; Best efficiency point
Characteristics of Centrifugal Pumps Working in Direct or Reverse Mode: Focus on the Unsteady Radial Thrust  [PDF]
Anthony Couzinet,Laurent Gros,Daniel Pierrat
International Journal of Rotating Machinery , 2013, DOI: 10.1155/2013/279049
Abstract: 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. 1. Introduction The hydraulic performances of centrifugal pumps were widely studied experimentally over the last century, for normal operating modes close to the nominal operating point. For specific states of flow, the unsteady behaviour of the flow due to the rotor/stator interactions formed the subject of many studies. The experimental study of these unsteady phenomena requires complex and/or expensive experimental methods [1–3] such as the use of dynamic pressure sensors or strain gauges installed on the pump shaft, and, as a result, the numerical approach becomes a real alternative. As a matter of fact, CFD computations have been commonly used for approximately twenty years to predict the hydraulic performance of rotating machines. First of all, CFD computations made it possible to study and improve the design of blades. For that purpose, the use of periodical conditions became a means to reduce the size of the computational domain as well as the CPU time. Furthermore, it was possible to use a steady state approach to study operating points located close to the best efficiency point. Then, to study the rotor/stator interactions, the complete geometry of the pump needs to be integrated into the numerical model; it is also necessary to simulate these flow configurations in a transient manner [1, 4] in order to correctly predict all potential hydrodynamic instabilities. Nevertheless, although many projects focus on rotor/stator interactions, very few of them propose comparisons between numerical and experimental results. The only existing results concern the fluctuating pressure field at impeller outlet [5]. Even if a few studies
Modeling MEMS With Matlab’s Simulink  [PDF]
Amir J. Majid
International Journal of Engineering , 2011,
Abstract: Matlab’s Simulink has been used to simulate a dynamic feedback MEMScomprising a generator with field winding, mechanical shaft system and encoderas well as a feedback to a referenced signal. The model of this system has beensuggested used in Simulink for simulation.
A Fatigue Analysis of a Hydraulic Francis Turbine Runner  [PDF]
Miriam Flores, Gustavo Urquiza, José María Rodríguez
World Journal of Mechanics (WJM) , 2012, DOI: 10.4236/wjm.2012.21004
Abstract: In this work, the estimation of crack initiation life of a hydraulic Francis turbine runner is presented. The life prediction is based on the local strain approach to predict the initiation life. First, the analysis is carried out in air and in water condition and the runner’s natural frequencies were calculated using the finite element (FE) method. The analysis in air is compared with experimental analysis in order to have a representative model of real runner and subsequently the numerical analysis was perform in water. In the case of the runner immersed in water, the added mass effect due to the fluid structure interaction (FSI) is considered. Second, the static and dynamic stresses were calculated according to life estimation. For the calculation of static stresses, the pressure distribution of water and the centrifugal forces were applied to the runner. The dynamic stresses were estimated for interactions between the guide vane and the runner. Lastly, the estimation of the crack initiation life of the runner was obtained.
Multimodel Robust Control for Hydraulic Turbine  [PDF]
Jakub Osusky,Stanislav ?tevo
Advances in Electrical Engineering , 2014, DOI: 10.1155/2014/512628
Abstract: The paper deals with the multimodel and robust control system design and their combination based on structure. Controller design will be done in the frequency domain with nominal performance specified by phase margin. Hydraulic turbine model is analyzed as system with unstructured uncertainty, and robust stability condition is included in controller design. Multimodel and robust control approaches are presented in detail on hydraulic turbine model. Control design approaches are compared and used for derivation of new approaches which combine advantages of both. 1. Introduction When hydraulic turbine power control is considered, the water inertia effect is a factor that makes it difficult to maintain stability under isolated operation or to have fast response in case of load change in the whole operational range. Nonlinear models of hydraulic turbine control systems are needed in those cases where the turbine power varies in the whole range. The turbine model parameters vary significantly with the unpredictable load variations. Such nonlinearities make the controller design a nontrivial task due to the fact that a controller designed for specific operating conditions may not perform well under different loads [1]. This fact leads to the adaptive [2] or hybrid control algorithms. There are several approaches to model hybrid systems [3]. In a model of a large class of hybrid systems, [4] is considered as discrete event system and continuous dynamic modeled by differential or difference equation. Such models are used to formulate a general stability analysis and controller synthesis framework for hybrid systems. Results for modeling and stability analysis of hybrid systems have been presented in [3, 5, 6]. In this paper, we follow the class of hybrid system known as switched systems [7]. In this paper, hybrid control, often denoted by multimodel control, will be used. Several switching algorithms will be compared to show how the switching speed affects performance and stability. Well-known robust control method will be presented as a control solution which ensures stability on whole operating range, but with lower performance. Combination of multimodel control and robust control which ensure stability and good performance will be presented on numerical example of nonlinear hydraulic turbine model. 2. Preliminaries and Problem Formulation Consider nonlinear system as uncertain system described by set of transfer functions and controller in standard configuration: where , , and are output, control, and set-point variables of system, respectively; is the
Online design of Matlab/Simulink block schemes
Zoltán Janík,Katarína ?áková
International Journal of Emerging Technologies in Learning (iJET) , 2011, DOI: 10.3991/ijet.v6is1.1614
Abstract: The paper presents a new online tool that enables to build a Matlab/Simulink block scheme in the Internet environment. The block scheme can be designed in similar manner as it is offered by local installation of Simulink. The application was created by widely used technologies as XHTML, CSS, JavaScript, PHP together with AJAX approach. The created application can be used as a supporting tool in virtual and remote laboratories.
International Journal of Engineering Science and Technology , 2010,
Abstract: With the growth of computational mechanics, the virtual hydraulic machines are becoming more and more realistic to get minor details of the flow, which are not possible in model testing. In present work, 3D turbulent real flow analyses in hydraulic Francis turbine have been carried out at three guide vane opening and different rotation speed using Ansys CFX computational fluid dynamics (CFD) software. The average values of flow parameters like velocities and flow angles at the inlet and outlet of runner, guide vane and stay vane of turbine are computed to derive flow characteristics.
First-Class Variability Modeling in Matlab/Simulink  [PDF]
Arne Haber,Carsten Kolassa,Peter Manhart,Pedram Mir Seyed Nazari,Bernhard Rumpe,Ina Schaefer
Computer Science , 2014, DOI: 10.1145/2430502.2430508
Abstract: Modern cars exist in an vast number of variants. Thus, variability has to be dealt with in all phases of the development process, in particular during model-based development of software-intensive functionality using Matlab/Simulink. Currently, variability is often encoded within a functional model leading to so called 150%-models which easily become very complex and do not scale for larger product lines. To counter these problems, we propose a modular variability modeling approach for Matlab/Simulink based on the concept of delta modeling [8, 9, 24]. A functional variant is described by a delta encapsulating a set of modifications. A sequence of deltas can be applied to a core product to derive the desired variant. We present a prototypical implementation, which is integrated into Matlab/Simulink and offers graphical editing of delta models.
MATLAB Simulink Simulation Platform for Photonic Transmission Systems  [PDF]
Le Nguyen BINH
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2009, DOI: 10.4236/ijcns.2009.22012
Abstract: High speed and ultra-high capacity optical communications have emerged as the essential techniques for backbone global information transmission networks. As the bit rate of the transmission system gets higher and higher 40 Gb/s to 100 Gb/s the modeling of proposed modulation techniques is very important so as to avoid costly practical demonstration. The search for a universal modeling platform for such systems is urgent. Matlab Simulink has become the universal mathematical and modeling tools in most universities and re-search laboratories around the world. This paper thus describes the modeling techniques for advanced photonic transmission systems and Simulink is proven to be very effective platform for development of photonic communications systems due its comprehensive blocksets. The simulation is based mainly on the physical phenomena and understanding of its concepts of communications and photonics. Simulink models are given as examples of various sub-systems of the photonic transmission systems. Some simulated trans-mission performances are demonstrated as examples of final results obtained from Simulink models of the transmission systems.
Modeling and Simulation of BLDCM Using MATLAB/SIMULINK
C.Gencer,M. Gedikpinar
Journal of Applied Sciences , 2006,
Abstract: The aim of this study was to modeling of three phases Brushless DC Motor (BLDCM) with MATLAB/SIMULINK package program. Brushless DC motors (BLDCM) have important advantages according to brushed DC motors and induction motors. They have better speed/torque characteristics, high efficiency, high dynamic response, small size construction and so on. The design and analysis of complex power electronic systems such as motor drives is usually done using a modern simulation software, such as MATLAB/SIMULINK, SPICE, EMTP, SABER, SPECTRE, SIMPLORER, etc., which can provide accurate predictions of the systems behavior in reality.
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