Numerical investigation of tongue effects on pump performance in direct and reverse modes

29th IAHR Symposium on Hydraulic Machinery and Systems

Arani, Hamed Alemi^1 ; Fathi, Mohammad^1 ; Raisee, Mehrdad^1 ; Nourbakhsh, Seyed Ahamd^1

Hydraulic Machinery Research Institute, School of Mechanical Engineering, College of Engineering, University of Tehran, P.O. Box 14395-515, Tehran, Iran^1

关键词: Efficiency increase;    K-Omega turbulence model;    Low specific speed centrifugal pump;    Numerical investigations;    Numerical results;    Pump performance;    Second order upwind scheme;    Transport equation;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/240/4/042003/pdf
DOI  :  10.1088/1755-1315/240/4/042003

来源: IOP

【 摘 要 】

This paper investigates the effects of tongue geometry on the performance and radial force of a low specific speed centrifugal pump in direct and reverse modes numerically. For the evaluation of unknown Reynolds stresses, the k-ω turbulence model was employed. The nonlinear convective terms in all transport equations were approximated by the second-order upwind scheme. The unstructured computation grid with 1.75×106 cells was used for the computation. Numerical results indicated that as expected, the tongue geometry significantly alters the performance and radial force in both direct and reverse modes. In the next step, the effects of two geometrical parameters of tongue, namely; tongue stretching and tongue angle were studied. The results obtained by CFD simulations in pump mode proved that the tongue with the most stretching yields the lowest head value in high flowrates and decreases efficiency. Moreover, it is found that the tongue with medium stretching has no sensible effect on the radial force, while one with the most stretching can increase the radial force significantly. In addition, this study proved that changing the tongue angle increases the radial force exerted on impeller and can lead to lower efficiencies in the pump. The numerical study of fluid flow in PAT mode revealed that by increasing the tongue stretching of a tongue while keeping the angle constant, both head and power increases. For the tongues with medium stretching, it is found there is no direct relation between tongue angle and head but by increasing the tongue angle both power and efficiency increase. In the tongue with the most stretching, the tongue with angle of -10° produced the highest power while that of -5° leads to the highest efficiencies in all flowrates.