The axial flow type turbines are available for hydraulic power resources of medium and low heads. It includes Propeller type (fixed blade type) and the Kaplan type (adjustable blade type) turbine. The Propeller type turbines are suitable for hydropower stations with small or medium capacities and heads, and relatively stable loads. The Kaplan turbines are suitable for hydropower stations with medium or large capacities and heads, and relatively unstable loads.
Kaplan model name: ZZ; Propeller model name: ZD
The diameter of the runner: 0.8m-8.0m;
Suitable water head: H =2m- 70m;
Suitable flow: Q =1.0m3/s- 200m3/s;
Capacity of the generator unit: 100kw -100MW.
The blades of Propeller are fixed on runner hub. The place angle of blades cannot be changed in operation. As its efficiency curve is relatively steep, it is suitable for small load change or the station to adjust the running amount of the units in order to adapt to the load variation. It has the advantages of simple structure and low cost; while the disadvantage is that its efficiency will decline sharply when deviating from the design condition. According to its characteristics, the axial fixed-blade turbine is commonly used in the hydropower station with small output, low water head and small head variations. The axial fixed-blade turbine has larger flow capacity and the improved cavitation performance than axial movable-blade turbine, but it cannot meet the requirements of the hydropower stations whose head and load change is too big. Its specific ratio speeds are 250~700 and applicable heads are 3~50m.
The Kaplan Turbine blade is usually operated by the oil pressure relay installed in the runner hug and can be turned according to head and load changes in order to keep the optimal coordination between the activity of the guide vane angle and the blade angle to enhance average efficiency. The maximum efficiency of this kind of turbine have been more than 94%. Its has the advantages of small size and light weight, while the disadvantage is easily limited flow capacity when available head increases, large cavitation coefficient, complicated structure, high cost. The axial movable-blade turbine is commonly used in the large and medium-sized hydropower station with output and head vary widely. Its specific speed is up to 200~850, which applies to the station of low head (3~80m) and large load change.
Main Parts: Blades, hub, main shaft, runner cone, rotating mechanism.
* Blade: Curved surface, airfoil section, thick root, and thin edge to bear the torque of water flow.
* Amount of blades: Related to H, generally 4~8 pieces.
* Blade rotating angle F: F=0°; when optimum operating condition, the blades begin to turn when F>0, the blades turn to close when F<0. -15°>F<+20°.
* Hub: Connected with blades externally, installed rotating mechanism internally.
* Rotating mechanism: It is installed inside the hub, controlled by governor, high-speed guide vane angle.