Hydraulic turbines for hydropower plants have been used since the nineteenth century. However, new and innovative turbines are being introduced to the market, in order to improve efficiency, and to extend the operational range of existing turbines. The so called M turbine was developed and patented in Italy (Patent 0000282352) by Eng. Mario Mariucci in October 2016, who is now scientifically cooperating with Eng. Emanuele Quaranta (Turin, Italy), to overcome the deficit of standard action turbines.
Innovation of the M Turbine
The M turbine is an action turbine, thus a hydraulic turbine that exploits the kinetic energy of a water jet. Furthermore, it is an axial flow machine, since the water jet flows parallel to the vertical rotation axis of the turbine (Fig.1). The M turbine that can work in hydraulic conditions where common action turbines (Pelton and Turgo turbines) cannot be convenient and efficient. Existing action turbines in very low head sites can exploit very small flow rates (few tens of liters per second), with very low power output. The M turbine can be employed in sites with heads (difference between the water level upstream and downstream of the turbine) less than 3 m and flow rates less than 3 m3/s (Source: Teti srl). The efficiency is between 85% and 90% for a wide range of flow rates.
Hence, the M turbine represents a suitable alternative to common action turbines in the micro hydropower field (power less than 100 kW), especially in sites with head differences less than 10 m.
How Does the M Turbine Work?
The M turbine is installed with a vertical rotation axis inside a tank, which is filled with water. The water free surface level of this tank corresponds to the upstream water level, while the downstream water level corresponds to the tailrace, as well as the water free surface in the river just under the turbine. At the center of the tank is an orifice, where the turbine is installed. Along the periphery of the wheel, there are the blades. The water flows from the tank to these blades, exerting a force on them, and determining the rotation of the turbine. The cross section through which the flow rate passes is a circular crown as large as the blades. Thanks to movable sheets, it is possible to regulate the portion of this cross section through which the water jet can flow (called effective area), so that the flow rate can be regulated. This means that when the available flow rate reduces, the effective area is also reduced by an external control; in this way, the head in the tank is maintained constant, as well as the flow velocity. As a consequence, the rotational speed of the turbine can be maintained constant, thus expensive electro-mechanic equipment to change the turbine velocity or blades inclination are unnecessary.
When the downstream water level increases, a lifting system lifts the turbine to avoid the turbine becoming immersed in water. In this way, the draft tube used in common reaction turbines is not required.
