139267
20190812205330.0
doi
10.1115/FEDSM2007-37550
ISI
000254289800149
CONF
Unsteady Numerical Simulations of the Flow Related to the Unstable Energy-Discharge Characteristic of a Medium Specific Speed Double Suction Pump
2007
2007
Conference Papers
Regions of positive slope in the pressure-discharge characteristics can result in a reduction or even lack of damping of system instabilities. They are therefore one of the major concerns in design and operation of centrifugal pumps as they are limiting the admissible operating range. The considered preliminary hydraulic design of an industrial double suction pump of medium specific speed n = 0.410 (0.205 per impeller side) shows a marked saddle in the energydischarge characteristic associated to a sudden drop of efficiency versus discharge at part load. Unsteady RANS type flow simulations are performed using hexahedral meshes with 2.5 million nodes to model the inlet casing, the shrouded double sided impeller with 2 x 7 blades, the diffuser with 12 blades and the volute. In unsteady solution monitoring, low frequency (below blade passing frequencies) phenomena are noticed. Therefore, simulation times of up to 10 impeller revolutions at each flow rate are requested to achieve statistically steady behavior of the flow judged on global performance numbers and circumferential flow rate distribution. The numerical simulations emphasize a drop in the characteristic, though at a lower flow rate than found on the test rig. It is shown to be associated to a one-sided separation in the diffuser, further leading to an unbalanced flow rate distribution of about 10% of flow rate between both sides of the impeller. There is a region of hysteresis, where both configurations with balanced and unbalanced flow rate distributions can be obtained for the same global flow rate. The asymmetric flow distribution leads to asymmetric velocity profiles at the impeller-diffuser interface which results in a strongly vortical flow in the diffuser channels, where an important amount of energy is dissipated in regions of increased viscous and turbulent shear.
Braun, Olivier
241012
Avellan, François
104417
243999
Dupont, Philippe
105022
ASME/JSME 2007 5th Joint Fluids Engineering Conference
San Diego, California, USA
July 30–August 2, 2007
2, part A-B, Fora
971-977
ASME Conf. Proc. FEDSM2007
825084
http://infoscience.epfl.ch/record/139267/files/FEDSM2007-37550.pdf
n/a
252135
LMH
U10309
oai:infoscience.tind.io:139267
STI
conf
GLOBAL_SET
148230
LMH-CONF-2009-004
EPFL
REVIEWED
PUBLISHED
CONF