TY - GEN
T1 - Numerical investigation of the influence of impeller-diffuser gap (A-and B-GaPs) on unsteady flow in a centrifugal pump at part flows
AU - Takamine, Taiki
AU - Watanabe, Satoshi
N1 - Funding Information:
This study has been carried out under the activity of WG2 in HPC (High Performance Computing) Research Committee of Turbomachinery Society of Japan (TSJ). The authors would like
Funding Information:
This study has been carried out under the activity of WG2 in HPC (High Performance Computing) Research Committee of Turbomachinery Society of Japan (TSJ). The authors would like to express sincere gratitude to the members of WG2 for fruitful discussions throughout WG2 meetings. The hydraulic design of the test pump was made by Miyagawa Lab. of Waseda University, Japan, and the staffs/students involved are highly appreciated for their contributions. A part of the computational grid used in the present study was provided by Dr. Hiroyoshi Watanabe of Ebara Corporation. Finally, we would like to thank to TSJ for the organization of the research committee and to DMW Corporation, Ebara Corporation, Hitachi, Ltd. and Shin Nippon Machinery Co. Ltd. for their financial supports.
Publisher Copyright:
Copyright © 2019 ASME.
PY - 2019
Y1 - 2019
N2 - Because of the high energy density of multi-stage centrifugal pump, it is really important to ensure the reliability of the pumps thus the stability of rotor system in the wide flow rate range. Rotating stall is a well-known unsteady flow phenomenon in which one or several stall cell structures propagate circumferentially in impeller and/or diffuser. Rotating stall alters the peripheral pressure distribution of rotors, and therefore it is often regarded as one of the primary trigger of unstable fluid force acting on the rotor system. One possible factor which could affect the rotating stall is a geometrical relationship between the rotor and the stator. In the present study, unsteady RANS simulations of internal flow in a centrifugal pump are carried out. The pump is the partial model of the final stage of the three-stage centrifugal pump used in our previous study. In order to investigate the effect of the gap between impeller trailing edge and diffuser leading edge on the unsteady flow of the pump, three cases of impeller-diffuser gap is simulated; one is the smaller gap case with original impeller. The other cases are two larger gap cases with only cutting the impeller blades and with cutting the both impeller blades and impeller shroud walls. For all gap cases, the computations are conducted for the nominal flow rate and the low flor rate with 10% of the nominal flow rate. As a result, the rotating stall is observed only in the larger gap case with the cut shroud walls, indicating that the key phenomenon for the stable formation of the stall cell is not only the weakened rotor-stator interaction, but also the other phenomenon attributed to the enlarged gap between the impeller shroud walls and the diffuser walls. In the shroud cut case, a part of the main flow blocked by the stalled region and the secondary flow on the diffuser walls tend to flow into the side gaps more easily than other cases. They might be the important phenomenon associated with the diffuser rotating stall in the enlarged wall gap condition.
AB - Because of the high energy density of multi-stage centrifugal pump, it is really important to ensure the reliability of the pumps thus the stability of rotor system in the wide flow rate range. Rotating stall is a well-known unsteady flow phenomenon in which one or several stall cell structures propagate circumferentially in impeller and/or diffuser. Rotating stall alters the peripheral pressure distribution of rotors, and therefore it is often regarded as one of the primary trigger of unstable fluid force acting on the rotor system. One possible factor which could affect the rotating stall is a geometrical relationship between the rotor and the stator. In the present study, unsteady RANS simulations of internal flow in a centrifugal pump are carried out. The pump is the partial model of the final stage of the three-stage centrifugal pump used in our previous study. In order to investigate the effect of the gap between impeller trailing edge and diffuser leading edge on the unsteady flow of the pump, three cases of impeller-diffuser gap is simulated; one is the smaller gap case with original impeller. The other cases are two larger gap cases with only cutting the impeller blades and with cutting the both impeller blades and impeller shroud walls. For all gap cases, the computations are conducted for the nominal flow rate and the low flor rate with 10% of the nominal flow rate. As a result, the rotating stall is observed only in the larger gap case with the cut shroud walls, indicating that the key phenomenon for the stable formation of the stall cell is not only the weakened rotor-stator interaction, but also the other phenomenon attributed to the enlarged gap between the impeller shroud walls and the diffuser walls. In the shroud cut case, a part of the main flow blocked by the stalled region and the secondary flow on the diffuser walls tend to flow into the side gaps more easily than other cases. They might be the important phenomenon associated with the diffuser rotating stall in the enlarged wall gap condition.
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U2 - 10.1115/AJKFluids2019-5372
DO - 10.1115/AJKFluids2019-5372
M3 - Conference contribution
AN - SCOPUS:85076681711
T3 - ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019
BT - Fluid Applications and Systems
PB - American Society of Mechanical Engineers (ASME)
T2 - ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019
Y2 - 28 July 2019 through 1 August 2019
ER -