Test rig operation of a pump as turbine

Whenever a pump’s flow is reversed, the rotational direction of the runner is inverted, and thus the original pump unit operates as turbine. Especially in the case of applications for which the costs of a conventional turbine – which is normally a prototype – are too high, a pump in turbine mode is quite suitable. As pumps are a serial product, the investment costs are lower, which compensates a possible lower efficiency when compared to a “genuine” turbine. On request of a pump manufacturer, a pump has been installed and tested for this kind of application in the Institute’s laboratory.

The measurements aimed at the identification of the test sample’s efficiency under different operating conditions, whereas the different operating points were set by the variation of flow and rotational speed. Furthermore, the cavitation behaviour of the model pump was examined. In order to be able to register the mechanical characteristics during operation mode, the model machine delivered by the manufacturer had to be adapted and equipped with a speed and a power meter. All remodelling work was performed by the Institute’s employees.

The measurements provided data on the performance of the tested model as well as suggestions for improvement measures which could easily be realised in order to increase the potential efficiency. Additionally, these tests generated new findings regarding the start-up behaviour of the pump in turbine mode.