Pico Turbine Testing Laboratory

Pico hydro power schemes with axial flow machines generate electricity or mechanical power by converting the energy available mainly in " Run-of-river", with the flow of water within the river's natural range and with no reservoir and with or without head. The axial flow turbine can generate power with or without head and low head sites are statistically much more common and are found in or near concentrations of population where there is a need and demand of electricity.
Pico hydro in rural areas of Nepal can replace the fuel-based power production and can boost the local economic development of isolated populations by producing autonomous and reliable energy that can be used for local lighting, agro-processing and water pumps.
The main challenge of Pico hydro is to reduced production, construction, operation and maintenance costs and secondly improving hydro and electro mechanical performances. It is therefore essential to have well-structured and coordinated Research in order to develop new machines and construction techniques which are simple, reliable and efficient. Current Research on KU on Pico Hydro includes: systemized design of turbines, testing of new construction materials, synchronous generators, variable speed generation, programmable logic controllers, and improving flow.

It was out of studies and enquiries that KU determined, with more urgency, to design and build (and indeed rebuild) a much cheaper and smaller facility for testing turbines and other pico gear up to 2kW capacity, and to contribute to the dearth of knowledge about how axial-axial pico machines really behave; and may be designed to actually achieve their design goals. Beyond that, we are involved in rural energy development programmes (eg., with Alex Zahnd in Humla) for which we will need many cheap reliable 0.4kW to 1.5kW hydro-generators that will do exactly what we claim they will do, and keep doing it! Beyond that again, it is a role of a university both to investigate natural and engineering fluid systems and machines and to make useful design expertise more readily available (especially in a ‘black art and guesswork’ field like cheap pico hydro).It now appears essential that we should undertake basic research on axial pico turbines, as there is such great potential for these in Nepal and some other Asian countries. In these notes we attempt to describe the features of the new laboratory, identify axial-flow pico turbine design problems, outline a practical design approach and show how we hope to obtain better data.

Laboratory Introduction

The KU laboratory is initially for testing vertical-shaft axial-flow turbines of 0.4 up to 2kW mechanical power output. As rebuilt, water is supplied (at present) by a 72-73litre/sec ‘centrifugal’ pump (pump heads are adjustable) from the bottom of either of two in-floor 4000litre tanks (one in fiberglass, one in steel) through butterfly control valves. Passing from the pump through a sluice-gate control valve (roughly calibrated), water is lifted to an overhead open flume (also built at KU in fiberglass) and passes through flow-straighteners (to remove surface waves and induce parallel flow at low Froude number) into an open spiral volute at the far end. This is designed to promote uniform peripheral entry of water, without troublesome minor vortices or waves, into the turbine sink. (This conical sink is exchangeable for others of different shape to allow experimental free vortices to be tested). Whirling water then passes into an annular sleeve in which different designs of inlet guide vanes can be tested, to direct water (induced whirl must vary with radius) into one of several experimental runners. Each turbine runner is shaft connected through a flexible joint and a shaft-torquemeter to an instrumented overhead IMAG/generator, which itself can be loaded by constant-resistance loads.


From the turbine annulus (we are standardizing on two or three annulus diameters and only two draft tubes) a draft tubes reduces discharge flow velocities, maintains the suction head below the turbine and restores water head to atmospheric. Total available heads (positive IGV head plus the draft tube suction head) from about 2.1 to 2.7m will be tested, though cavitation must be of negligible effect at the modest flow and blade velocities prevailing.
Water discharging from the draft tube into an above-floor tank is stabilized and passed into a smaller flume, with another bank of flow straighteners and ending at a calibrated V-notch weir for quick determination of flowrates, discharging into one of the 4000litre in-floor tanks. The V-notche is itself calibrated by rate-of-fill measurements of either in-floor tank. One of these in-floor tanks is equipped with a steady-level depth tube containing float and above-floor depth indicator, and will have stiffened walls to ensure we know its volumes at any depth.

Pico axial flow propeller turbine under test

 

Developed by: Prakash Gautam and Supported by: Suman Aryal

 

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International Training Program on "Design and Installation of Micro-hydro Power Plant".

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-Held at Kathmandu University Dhulikhel from 18 March -31 March 2008.
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-Held at Kathmandu University C.V. Raman auditorium hall, Dhulikhel on May 7, 2008
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A one day Seminar was organized jointly by School of Engineering, Kathmandu University and AEPC, Nepal.

-Held at Kathmandu University International Centre, Dhulikhel on April 27, 2007
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