Determination of the parameters of an axial pico-hydroturbine for various operating regimes
S.I. Shtork1,2, I.V. Litvinov1,2, E.Yu. Gorelikov1,2, D.A. Suslov1,2
1Novosibirsk State University, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Keywords: pico-hydroturbine, axial turbine, laser Doppler anemometer (LDA), swirling parameter, hydro-turbine efficiency
Abstract
The paper presents the results of detailed experimental studies of the flow characteristics behind the impeller of an air model of a propeller-type pico-hydroturbine with an impeller diameter of 0.1 m. Using the method of laser-Doppler anemometry, distributions of two components of averaged velocities and pulsations were measured under the conditions varying from partial load to severe overload. It is shown that when the regime of hydroturbine operating deviates from the optimal one, the flow at the impeller outlet becomes swirling. Based on the data obtained, the character of evolution of the integral swirling parameter, which determines the swirling flow state, has been revealed. A trend for a sharp increase in the swirling parameter with a decrease in the air flow rate was found. Due to this increase, the degree of swirling reaches quickly a critical level at which the vortex disintegrates with the development of a central dip in the axial velocity profile and displacement of the flow to the channel walls. With an increase in the flow rate, a slower increase in the swirling parameter takes place, which remains below the threshold value even for a large overload. As a result, the maxima of the tangential velocity are located near the flow axis, and the profile of the axial velocity remains uniform over the flow cross section. Information about the flow characteristics can be used when adjusting the hydraulic unit regime to optimal conditions and developing recommendations for expanding the range of regulation of the hydroturbine operation while maintaining high efficiency.
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