Classical hydraulic ram pump performance in comparison with modern hydro-turbine pumps for low drive heads

Abstract

We present a unique comparison of two types of renewable hydro pumping devices, namely the ram and turbine pump having different working principles. This comparison is based on experiments with these pumping devices at a field station in a village in central-east India. Our work identifies the major gaps in the study of large ram pumps, covering the hydraulic scaling conformance to creation of a unified platform for the investigation of such pumping devices with respect to operating parameters like head, flow, efficiency and, most importantly, size. The field tests of ram revealed that its non-dimensional performance parameters fit perfectly on the theoretical scaling curves. The investigations further showed that while rams had more efficiency (53–62%), they could not handle more than 40–50 l/s of discharge. In comparison, the turbine pumps, tested in laboratory conditions, were more compact for flows beyond 100 l/s, but they settled for overall efficiencies between 49% and 55%. The study recommends a limiting design flow line for rams to be 50 l/s because of the size-factor. It further finds that for absolute flows between 50 and 100 l/s within the low-head range of 3–5 meters, the design of geometrical shapes for turbine pumps could be a challenge for optimized efficiencies. The head-discharge-diameter (H-Q-D) chart developed here is a useful way of interpreting the technology with respect to boundary conditions and it creates a roadmap for future inventions in such renewable hydro-pumping devices. The paper makes a case for axial flow pumps as turbines. It concludes with a call for the propagation of research on such nature-friendly pumping technologies, where most (90–95%) of the water is returned to the stream, paving the way for a new era of sustainability.