The paper provides the detail analysis of the causes of various types of the vortex motion of the turbulent flow in the inlet parts of the turbine and in the inter-blade channels of the runner. The causes of the appearance of large-scale vortex structures in the meridional sections of the spiral case of radial-axial hydraulic turbines with the heads of 400-500 m are shown. As a result of this phenomenon, in the section of the spiral case the flow is directed in the region of the walls to the runner. In the central part it is directed from the runner, i. e. the spiral case executing its functions of supplying the flow functions only with part of its section-the near-wall zone-where the vortex near-wall flow with increased velocity and energy losses enters to the channels of the runner. These conclusions in the work are argued by extensive experimental data. Energy losses in the spiral case reaches 3-5 % and a complex vortex structure, which enters to the runner, leads to a decrease of the energy characteristics. The flow inlet to the runner using nozzle devices located on the ring in front of the runner is considered in the paper. These nozzle devices increase the velocity by five or more times and provide low losses in the inlet (about 0,5 %) and almost uniform flow in front of the runner with a moment of quantity of motion, which provides an optimal operation of the hydraulic turbine. The improvement of the working flow and control systems is presented in this paper using new design solutions, for which more than ten patents of Ukraine for the invention were obtained. In particular, as a result of this study of the working processes of Francis-Deriaz hydraulic turbines, which allowed the use of blade turbines for the heads of more than 400-500 m up to 800-1000 m with high energy and cavitation characteristics with wide operating areas in terms of rates (powers) and heads, with an increase of 2-7 % average operating efficiency. The working process of a new type of diagonal-axial hydraulic turbine with a very wide operation range in terms of flow and pressure with a significantly increased average operating efficiency, increased operation reliability, which is illustrated by the predictive universal characteristic, is also considered. This characteristic allows the use of rotary-blade hydraulic turbines for heads up to 230-250 m. Therefore, the carried out improvement of the working process of hydraulic turbines and their control systems convincingly proves the advantage of the new scientific and technical solutions in comparison with previously used ones.
The article deals with new design solutions to improve the operating process based on new design solutions and effectively use hydraulic turbines for heads up to 800-1000 m, expand the operating range relative to flow rates and heads with high energy and cavitation indicators and reliability of operation on varying modes that differ from the optimum operating mode. On the basis of complex experimental studies of the flow pattern in a water passage and, first of all, in the hydraulic turbine inlet for heads of 400-500 m, this article reveals the causes of increased energy losses. The energy losses are caused by large vortexes occurring in the spiral casing; they distort the flow directed to the runner of the hydraulic turbine. Several ways for improving the operating process are proposed, including new design solutions. The issues of improving the operating process of various types of hydraulic turbines are discussed. This is done by creating an angular momentum upstream the runner blades, which is necessary for optimum operation of the hydraulic turbine due to flow inlet using nozzle vanes located around of the runner inlet. The advantages of new types of hydraulic turbines and a more advanced operating process are illustrated by the hill diagram of this turbine.
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