Hydraulic Turbine Dr Rajendra Shrestha Introduction n n

Hydraulic Turbine Dr. Rajendra Shrestha

Introduction: n n Fluid machines are the m/C that converts the fluid energy to mechanical/ electrical or vise versa. Pump: add energy to fluid Turbine extract energy from fluid A hydraulic turbine is a prime mover that uses the energy of flowing water and converts it into the mechanical energy (in the form of rotation of the runner).

Introduction: n Conventional and renewable A good environmental effect Large investments n Long gestation period n n

Classification of Hydraulic Turbine n n n 1. According to the head and quantity of water available Impulse turbine. . . requires high head and small quantity of flow. Reaction turbine. . . requires low head and high rate of flow, medium head and medium flow, low head and

2. According to the name of the originator 1. Pelton turbine. . . named after Lester Allen Pelton of California (U. S. A). It is an is impulse type of turbine and is used for high head and low discharge. 2. Francis turbine. . . named after James Bichens Francis. It is a reaction type of turbine from medium high to medium low heads and medium small to medium large quantities of water. 3. Kaplan turbine. . . named after Dr. Victor Kaplan. It is a reaction type of turbine for low heads and large quantities of flow.

3. According to action of water on the moving blades n n Impulse turbine-Pelton turbine Reaction turbine- Francis turbine, Kaplan and propeller turbines

4. According to direction of flow of water in the runner 1. Tangential flow turbines (Pelton turbine) the water strikes the runner tangential to the path of rotation. 2. Radial flow turbine (no more used) 3. Axial flow turbine (Kaplan turbine ) water flows parallel to the axis of the turbine shaft. 4. Mixed (radial and axial) flow turbine (Francis turbine) the water enters the blades radially and comes out axially, parallel to the turbine shaft. Modem Francis turbines have mixed flow runners.

5. According to the position of the turbine shaft n Turbine shaft may be either vertical or horizontal. In modern practice, Pelton turbines usually have horizontal shafts whereas the rest, especially the large units, have vertical shafts.

6. According to specific speed n The specific speed of a turbine is defined as the speed of a geometrically similar turbine that would develop 1 k. W under 1 m head. All geometrically similar turbines (irrespective of the sizes) will have the same specific speeds when operating under the same head

6. According to specific speed contd. n n n Ns=NP 1/2/ H 5/4 N= the normal working speed, P= power output of the turbine, and H= the net or effective head in metres. Turbines with low specific speeds work under high head and low discharge conditions. High specific speed turbines work under low head and high discharge conditions.

Comparison of turbines: Pelton Frances Kaplan 100 -1700 80 -500 Up to 400 Maximum power 55 output (MW) 40 30 Best efficiency 94 94 Guide vanes, surge tank Operating head, m 93 Regulation mech. Spear nozzle and deflector plate