CROSS FLOW TURBINE

This impulse turbine, also known as Banki-Michell in remembrance of its inventors and Ossberger after a company which has been making it for more than 50 years, is used for a wide range of heads overlapping those of Kaplan, Francis and Pelton. It can operate with discharges between 20 litres/sec and 10 m3/sec and heads between 1 and 200 m. Water (figure 6.7) enters the turbine, directed by one or more guide-vanes located in a transition piece upstream of the runner, and through the first stage of the runner which runs full with a small degree of reaction. Flow leaving the first stage attempt to crosses the open centre of the turbine. As the flow enters the second stage, a compromise direction is achieved which causes significant shock losses. The runner is built from two or more parallel disks connected near their rims by a series of curved blades). Their efficiency is lower than conventional turbines, but remains at practically the same level for a wide range of flows and heads (typically about 80%).

Turbine Design Parameters

Site Data

According to the head, schemes can be classified in three categories:

. High head: 100-m and above

. Medium head: 30 - 100 m

. Low head: 2 - 30 m

The site under consideration in the present work for installing a turbine is located in hyber Pakhtunkhwa with a head of 13.6m and can thus be categorized as a low head site. The volumetric flow rate available is 0.206m³/s.

Theoretical Power Output

The theoretical power output is an assumption of the energy potential of the site with alue of the micro-hydro scheme. It can be calculated using the site head and volumetric flow rate. Following formula is true for the calculation of theoretical power output:

P_t = γηHQ

With an assumption of 80% efficiency, the theoretical power output comes out to be:

P_t = 21.94kW