Bulb turbines
The solution for very low head applications with a net head range from 0.5 to 30 m
Nowadays, very low heads can be used for power generation in a way that is economically feasible. So far, ANDRITZ HYDRO has supplied more than 300 units, ranging from heads of up to 30 m, with a maximum runner diameter of 7,700 mm and outputs up to 76.5 MW.
The most important feature of a bulb turbine is the horizontal positioning of the shaft, which results in a reduced size compared to a vertical shaft arrangement.
After the intake, the water passes through the moveable wicket gates, which are another device besides the runner for adjusting the water discharge and, as a result, the turbine output. Levers and links connect the wicket gates to the regulating ring, which is moved by two double acting servomotors. After passing the runner, the water exits from the turbine through the draft tube.
The generator is located in a watertight housing called the “bulb”.
For hydropower stations with very low heads, it is sometimes more economical to use a pit turbine/generator concept. A step-up gearbox increases the speed of the generator to make this component more compact and, therefore, less expensive. This will increase the overall feasibility of these projects.
The total installed capacity amounts to approximately 6,500 MW. Covering a market share of more than 70%, ANDRITZ HYDRO is the leader worldwide in bulb turbine/generator units.
