Volume 17, Issue 8 (10-2017)
Modares Mechanical Engineering 2017, 17(8): 360-368 |
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SAEMI S, Raisee M, Cervantes M, Nourbakhsh A. The evaluation of friction models to calculate the flow rate in pressure-time method. Modares Mechanical Engineering 2017; 17 (8) :360-368
URL: http://mme.modares.ac.ir/article-15-12130-en.html
URL: http://mme.modares.ac.ir/article-15-12130-en.html
1- School of Mechanical Engineering, College of Engineering
2- Faculty member, school of mechanical engineering, university of Tehran
3- faculty member of Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics Luleå University of Technology
2- Faculty member, school of mechanical engineering, university of Tehran
3- faculty member of Division of Fluid and Experimental Mechanics, Department of Engineering Sciences and Mathematics Luleå University of Technology
Abstract: (4139 Views)
The pressure-time method is a flow rate measurement technique generally employed in hydropower plants to evaluate the efficiency of hydraulic turbines. The 1D numerical simulation incorporating the finite volume method is employed to evaluate the method. The results are compared with the experimental data. The flow is simulated inside a straight pipe with Reynolds number Re=6.76×〖10〗^6. The flow rate reduction curve is employed for the simulation of the deceleration part of the flow, before valve closure, in the pressure-time method. The effective parameters on the flow rate calculation including the friction losses and the definition of the final time of the valve closure are studied in detail. The increase in the accuracy of the flow rate calculation is a function of the increase in the accuracy of the friction loss calculations. The effect of several friction factors proposed for the evaluation of the unsteady flow is studied on the accuracy of the flow rate calculation. The Pezzinga friction factor shows the least error in the flow rate calculation. The available methods to find out the final time of integration still show a large error. A new method is proposed for the flow rate estimation without any need to have the exact time of the valve closure with an acceptable accuracy.
Keywords: Pressure loss calculation, pressure-time method, final time of integration, transient analysis, flow rate calculation
Article Type: Research Article |
Subject:
CFD
Received: 2017/05/7 | Accepted: 2017/07/10 | Published: 2017/08/18
Received: 2017/05/7 | Accepted: 2017/07/10 | Published: 2017/08/18
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