Analysis of the internal flow behavior on S-shaped region of a Francis pump turbine on turbine mode

Abstract

2016),"Analysis of the internal flow behavior on S-shaped region of a Francis pump turbine on turbine mode", Engineering Computations, Vol. 33 Iss 2 pp. 543 -561 Permanent link to this document: http://dx.(2016),"A new strain-based finite element for plane elasticity problems", Engineering Computations, Vol. 33 Iss 2 pp. 562-579 http://dx.(2016),"A computational and experimental study for the optimum reinforcement layout design of an RC frame", Engineering Computations, Vol. 33 Iss 2 pp. 507-527 http://dx.If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services. AbstractPurpose -The purpose of this paper is to numerically analyze the flow characteristic and to explore the hydrodynamic mechanism of the S-shaped region formation of a Francis pump-turbine. Design/methodology/approach -Three-dimensional steady and unsteady simulations were performed for a number of operating conditions at the optimal guide vanes opening. The steady Reynolds averaged Navier-Stokes equations with the SST turbulence model were solved to model the internal flow within the entire flow passage. The predicted discharge-speed curve agrees well with the model test at generating mode. This paper compared the hydrodynamic characteristics of for off-design cases in S-shaped region with the optimal operating case, and more analysis focusses particularly on very low positive and negative discharge cases with the same unit speed. Findings -At runaway case toward smaller discharge, the relative circumferential velocity becomes stronger in the vaneless, which generates the "water ring" and blocks the flow between guide vane and runner. The runner inlet attack angle becomes larger, and the runner blade passages nearly filled with flow separation and vortexes. The deterioration of runner blade flow leads to the dramatic decrease of runner torque, which tends to reduce the runner rotation speed. In this situation, the internal flow cannot maintain the larger rotating speed at very low positive discharge cases, so the unit discharge-speed curves bend to S-shaped near runaway case. Originality/value -The analysis method of four off-design cases on S-shaped region with the comparison of optimal operation case and the calculated attack angles are adopted to explore the mechanism of S characteristic. The flow characteristic and quantitative analysis all explain the bending of the unit discharge-speed curves.

Research on an Output Power Model of a Doubly-Fed Variable-Speed Pumped Storage Unit with Switching Process

“…There are two ways to start a DFVSPS unit in generating mode. The following is illustrated by combining the motion equation of DFIM shown in Formula (9).…”

“…In Refs. [8,9], the S-shaped region of pump turbine was analyzed. Flow characteristics of the transient power interruption process of a prototype pump-turbine at pump mode were studied in Ref.…”

Role of blade rotational angle on energy performance and pressure fluctuation of a mixed-flow pump

“…Feng et al 23 conducted numerical simulation and 2D laser Doppler velocimetry measurements to study the unsteady flow in a low-specific speed radial diffuser pump. Xiao et al 24,25 experimentally and numerically investigated the relationship between pressure fluctuation and operation condition of a Francis pump turbine.…”

Pressure fluctuation and flow pattern of a mixed-flow pump under design and off-design conditions

“…The experimental data indicate that the pressure fluctuations have resulted from the superposition of the hydraulic disturbances and the interaction of blade and volute tongue. Xiao et al 9,10 numerically analyse the flow characteristic of the S-shaped region formation of a Francis pump-turbine, and figure out that at runaway case toward smaller discharge the relative circumferential velocity becomes stronger in the vaneless and blocks the flow between guide vane and runner. Tan et al [11][12][13][14][15] experimentally and numerically investigate the performance of pump under noncavitation and cavitation conditions, and figure out that the dominant frequency and amplitude of pressure fluctuation under off-design flow rates are different from that of design condition.…”

“…Xiao et al. 9,10 numerically analyse the flow characteristic of the S-shaped region formation of a Francis pump-turbine, and figure out that at runaway case toward smaller discharge the relative circumferential velocity becomes stronger in the vaneless and blocks the flow between guide vane and runner. Tan et al.…”