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Title: A double-acting hydraulic ram pump for deep-well water pumping
Author: Law, Thomas Robert
ISNI:       0000 0004 6063 3715
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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Many existing deep-well water pumping technologies that are affordable to developing world smallholders suffer from reliability issues, low efficiency and/or expensive running costs. The Double-Acting Hydraulic Ram Pump (DAHR) has the potential to address these problems. An evolution of the classic hydraulic ram pump that converts kinetic energy from free-flowing water sources into a reduced flow at a much higher head, the DAHR contains virtually no moving parts or dynamic seals. The result is a deep-lift technology that can be both highly efficient and extremely reliable. This thesis investigates the potential of the DAHR, taking an initial proof-of-concept rig to a design that is ready for outdoor field trials. The beta prototype design process has been aided considerably by the development of a suite of numerical models. Like the conventional hydraulic ram, the DAHR has clearly defined acceleration and delivery phases either side of an impact event. The fluid motion during acceleration is modelled using a 1D lumped element approach whereas the delivery phase modelling is based on the shock equations for both compression and rarefaction waves. Unlike the conventional hydraulic ram, the DAHR makes full use of the kinetic energy downstream of the impact. The numerical results facilitate the selection of drive pipe diameter, inlet/delivery valves and the choice of pipe material via the resulting sound speed. A 15 m tall test facility housed within a three storey public stairwell was set up to help simulate pumping from deep underground. The DAHR sitting in a tank at the bottom would lift water to the top of the stairwell before it was returned under gravity to complete the circuit. The driving power input to create the low pressure, high volume oscillatory flow within the DAHR U-tube is provided by two custom-made pneumatic fluidynes. The data acquired over several weeks of testing with three different plastic drive pipe materials required an automated post-processing routine capable of analysing DAHR performance impact-by-impact. Computed efficiencies of up to 75 percent were achieved while pumping 350 L/h at 32 m head. Experimental observations also showed good agreement with numerical modelling. A single-acting design, capable of fitting down a smaller borehole, was considered as an alternative way forward. A further prototype, with the second drive pipe replaced by a gas spring, was designed, built and tested in the same facility. The prototype proved substantially more difficult to control and estimated efficiency was approximately half that of the DAHR validating the original double-acting approach.
Supervisor: Stone, Richard Sponsor: Thermofluidics Ltd
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available