Impulse turbines are one of the major types of turbines, along with reaction turbines. Impulse turbines operate based on the concept of velocity, namely by changing the direction of a jet of either fluid or gas. This impulse in turn rotates the turbine and creates energy. Within this major type, several sub-types of impulse turbines exist, each going about this same task in a slightly different way.
Pelton turbines are designed with a number of cup-shaped components connected around the circumference of a runner that is in turn connected to a central hub. Nozzles are positioned all around the runner, and they inject water into these cups, which change the potential energy of the water into kinetic energy by pushing the turbine's wheel around. Pelton turbines may include different generations of the same cup-and-wheel apparatus, each an iteration of which creates a greater level of energy efficiency.
Turgo turbines are a variation of Pelton turbines. However, instead of full cups, Turgo turbines have only half cups around the runner. The presence of these half-cups allows the water to enter and exit the cups faster and in greater amounts than with Pelton turbines, thereby providing it with a much higher level of energy efficiency. Turgo turbines can be installed horizontally as well as vertically, while Pelton turbines can only be installed vertically.
Crossflow Water Turbines
Crossflow water turbines are designed with many trough-shaped blades in a radial arrangement around a cylinder-shaped runner. They are tapered at the water inlet as well as the blades' ends to ensure that the water flows as smoothly as possible. Crossflow turbines have only two nozzles, which shoot water at a 45-degree angle to the blades, thus converting the force into kinetic energy. A controlling mechanism regulates the flow of the water out of the nozzle. These turbines are drum-shaped. The water in these turbines actually passes through the blades twice, once from the outside of the blades to the inside, and another time from the inside to the outside. Crossflow turbines can usually handle a greater amount of water flow than Pelton turbines. They are also sometimes referred to as Michell-Banki or Ossberger turbines.