Investigation of simulation of axial pump as turbine (PAT) using different turbulence models

Bozorgi, A; Riasi, A; Nourbakhsh, A

Small hydropower stations as renewable resources of energy have noticeable potential in the world and with increasing energy demands, using such potentials is a need especially in many developing countries. The major problems of installing the new small hydropower stations are their high specific cost expressed in $/kW installed capacity and maintenance expenses. Part of the solution of these economic problems is to ubstitute the conventional turbines by simple and inexpensive machines such as reversible pumps. Industrial pumps can be effectively operated as turbines, but with lower efficiency comparing to the conventional turbines. From an economical point of view, using pumps as turbines can thus be recommended for power stations under 500 KW installed capacity. For heads ranged between 1 and 5 m and flow rated between 50 and 1000 lit/s, axial pumps can be used as turbines. In this work, an axial pump is simulated in reverse mode by computational fluid dynamics. Reynolds-Averaged Navier–Stokes equations are solved using different low-Reynolds number turbulence models. Characteristic curves of the reverse pump are obtained for each turbulence model and results are compared with experimental data to investigate ability of the models in simulation of this new application. The results show that Spallart- Allmaras and Launder-Sharma are suitable for investigation of operation of the axial PAT. Spalart-Allmaras model is preferred because convergence rate of this model is better.