The internal flow field in a centrifugal pump with specific speed of 84.5 was numerically simulated by using CFD method when it was operated as a pump and run reversely as a hydro-turbine. The Rey-nolds time-averaged Navier-Stokes equations, standard k-ε two-equation turbulence model and SIMPLEC method were adopted in the simulations. The radial thrust was calculated under different flow conditions in that both modes. It was confirmed that the radial thrusts predicted in pump mode is in good agreement with those estimated by means of the Stepanoff empirical correlation, suggesting the flow models adopted are correct and reasonable. It was shown that the best efficiency in turbine mode is lower than the pump mode by about 5.4% and the radial thrust in the turbine mode is always smaller than the pump mode at the same flow rate. In the turbine mode, the radial thrust rises with increasing flow rate. The angle of radial thrust vector measured from the volute tongue is reduced to 125° from 146° as flow rate increase up to 1.1 times the design flow rate in the turbine mode. When flow rate is higher than 1.1 times the design flow rate, however, the angle is increased with increasing flow rate. As a result, the angle is as large as 144° at 1.4 times the design flow rate. The results suggest that the strength of the pump shaft is strong enough and still can meet the requirement of operation in the turbine mode.
YANG Jun-Hu,LI Hai-Long,GONG Chao-Hui et al. Radial thrust behavior in centrifugal pump as hydro-turbine[J]. Journal of Drainage and Irrigation Machinery Engin, 2014, 32(1): 12-16.
Himanshu Nautiyal,Varun,Anoop Kumar,et al. Experimental investigation of centrifugal pump working as turbine for small hydropower systems[J]. Energy Science and Technology,2011,1(1):79-86.
Shahram Derakhshan,Ahmad Nourbakhsh. Experimental study of characteristic curves of centrifugal pumps wor-king as turbines in different specific speeds[J].Experimental Thermal and Fluid Science,2008,32(1):800-807.
Shahram Derakhshan,Ahmad Nourbakhsh. Theoretical,numerical and experimental investigation of centrifugal pumps in reverse operation[J]. Experimental Thermal and Fluid Science,2008,32(1):1620-1627.
Sonia Rawal, Kshirsagar J T. Numerical simulation on a pump operating in a turbine mode[C]//Proceedings of the Twenty-third International Pump Users Symposium,2007:21-27.