Reaction turbine can be divided into Francis turbine, axial turbine, diagonal turbine and tubular turbine. In the Francis turbine, the water flows radially into the water guide mechanism and axially out of the runner; In the axial flow turbine, the water flows into the guide vane radially and into and out of the runner axially; In the diagonal flow turbine, the water flows into the guide vane radially and into the runner in the direction inclined to a certain angle of the main shaft, or into the guide vane and runner in the direction inclined to the main shaft; In the tubular turbine, the water flows into the guide vane and runner along the axial direction. Axial flow turbine, tubular turbine and diagonal flow turbine can also be divided into fixed propeller type and rotating propeller type according to their structure. Fixed paddle runner blades are fixed; The rotor blade of the propeller type can rotate around the blade shaft during operation to adapt to the changes of water head and load.
Various types of reaction turbines are equipped with water inlet devices. The water inlet devices of large and medium-sized vertical shaft reaction turbines are generally composed of volute, fixed guide vane and movable guide vane. The function of volute is to evenly distribute the water flow around the runner. When the water head is below 40m, the spiral case of the hydraulic turbine is usually cast by reinforced concrete on site; When the water head is higher than 40m, the metal spiral case of butt welding or integral casting is often used.
In the reaction turbine, the water flow fills the whole runner channel, and all blades are affected by the water flow at the same time. Therefore, under the same head, the runner diameter is smaller than that of the impulse turbine. Their efficiency is also higher than that of impulse turbine, but when the load changes, the efficiency of turbine is affected to varying degrees.
All reaction turbines are equipped with draft tubes, which are used to recover the kinetic energy of the water flow at the runner outlet; Discharge the water downstream; When the installation position of the runner is higher than the downstream water level, this potential energy is converted into pressure energy for recovery. For the hydraulic turbine with low head and large flow, the outlet kinetic energy of the runner is relatively large, and the recovery performance of the draft tube has a significant impact on the efficiency of the hydraulic turbine.
Post time: May-11-2022