turbines numericals
Embed Size (px)
TRANSCRIPT

8/10/2019 Turbines Numericals
1/14

8/10/2019 Turbines Numericals
2/14
1 PELTON TURBINE VELOCITY TRIANGLES
A 137 mm diameter jet of water issuing from a nozzle impinges on
the buckets of a Pelton turbine, and is deflected through an angle of
165 0 by the buckets. Head available at the nozzle is 400 m.
Assume: C v = 0.97, speed ratio = 0.46; reduction in relative velocity
= 15 . Determine
a) Force developed by the jet on the runner
b) Power developed
c) Hydraulic efficiency of the turbine

8/10/2019 Turbines Numericals
3/14
2 PELTON TURBINE VELOCITY TRIANGLES
A Pelton Turbine works under a gross head of 400 m. The jet
diameter is 80 mm and the penstock diameter is 0.6m with length
of 4 km. The buckets deflects the jet through 165 and reduces
the relative velocity by 15 . Assume mechanical efficiency of 90 ,
determine:
a) Flow rate
b) Shaft power developed by the pump
c) Overall efficiency

8/10/2019 Turbines Numericals
4/14
PELTON TURBINE DESIGN

8/10/2019 Turbines Numericals
5/14
3 PELTON TURBINE DESIGN
A Pelton Turbine is required to drive a generator to develop 10 MW
of power. Available head at the nozzle is 760 m. Assume electricgeneration efficiency of 95 and Pelton wheel efficiency of 87 .
The jet after striking the blades, deflects by 165 0 with a 15 loss
in velocity due to blade friction. Assume C v = 0.97 and K u = 0.46.
Determine:
a) Flow through Nozzle
b) Diameter of the jet
c) Force exerted by Jet on the bucketd) Best synchronous speed for generation at 50 Hz;
Corresponding bucket diameter (Jet ratio = 10)

8/10/2019 Turbines Numericals
6/14
4 PELTON TURBINE DESIGN
Design a Pelton Turbine for the following specifications:
SHP = 9560 kWHead = 350 m
Speed = 750 rpm
Overall Efficiency = 85
Jet ratio (m) = 1/6
Cv = 0.985
Ku = 0.45

8/10/2019 Turbines Numericals
7/14

8/10/2019 Turbines Numericals
8/14
5 FRANCIS TURBINE VELOCITY TRIANGLES
Francis Turbine Inward Flow Reaction Turbine
An inward flow reaction turbine has external and internal diametersas 0.9 and 0.45 m. Turbine is running at 200 rpm, width of the
turbine at inlet is 200 mm. Velocity of flow through the runner is
constant, and is 1.8 m/s. Guide blades makes an angle of 10 0 at
the inlet, and discharge at the outlet of the turbine is radial. Find:
a) Components of velocity triangle at inlet and outlet
b) Power developed by the runner
c) Hydraulic efficiency

8/10/2019 Turbines Numericals
9/14

8/10/2019 Turbines Numericals
10/14
6 FRANCIS TURBINE DESIGN
Francis Turbine Inward Flow Reaction Turbine
Design a Francis Turbine for following specifications:Net head = 60 m
Speed = 700 rpm
Shaft Power = 294.3 kW
Overall Eff. = 84 ; Hyd. Efficiency = 93
Flow ratio = 0.2
Breadth Ratio = 0.2
Outlet Dia = 0.5 Inlet diaVane thickness = 5 of runner circumference
Velocity of flow at inlet and out are the same
Discharge is radial at the outlet

8/10/2019 Turbines Numericals
11/14
GEOMETRICALLY SIMILAR TURBINES
Specific Speed of a Turbine The speed of a turbine which is
identical in shape geometric dimension blade angle gateopening etc. but of such a size that it develops unit power when
working under unit head

8/10/2019 Turbines Numericals
12/14
FOR THE SAME TURBINE DIFFERENT CONDITIONS
Unit Speed (N u) = /
Unit Discharge (Q u) = /
Unit Power (P u) = /

8/10/2019 Turbines Numericals
13/14
7 UNIT QUANTITIES
A Turbine is to operate under a head of 25 m at 200 rpm. The
discharge is 9 cumecs. If the overall efficiency is 90 , determine
the performance of the turbine under a head of 20 m.

8/10/2019 Turbines Numericals
14/14
8 DRAFT TUBE
In a Francis turbine ,the velocity at the entrance and exit of the
draft tube are 6 m/s and 1.2 m/s. For a friction loss of 0.1 m,
and a tail water of 5 m below the entrance of the draft tube,
determine the pressure at inlet of the draft tube.