Design of stay vanes and spiral casing

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# Design of stay vanes and spiral casing - PowerPoint PPT Presentation

Design of stay vanes and spiral casing. Revelstoke, CANADA. Guri-2, VENEZUELA. Aguila, ARGENTINA. Sauchelle-Huebra, SPAIN. Sauchelle-Huebra, SPAIN. Three Gorges Turbine, GE Hydro. The spiral casing will distribute the water equally around the stay vanes

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Presentation Transcript

In order to achieve a uniform flow in to the runner, the flow has to be uniform in to the stay vanes.

Streamline

Flow in a curved channel

m

Newton 2. Law gives:

1

The Bernoulli equation gives:

Derivation of the Bernoulli equation gives:

2

Example

C

L4

Flow Rate Q = 1,0 m3/s

Velocity C = 10 m/s

Height By = 0,2 m

Radius R0 = 0,8 m

Find: L1, L2, L3 and L4

L1

q

L3

R0

R

L2

By

Example

C

L4

Flow Rate Q = 1,0 m3/s

Velocity C = 10 m/s

Height By = 0,2 m

Radius R0 = 0,8 m

L1

q

L3

R0

R

L2

By

Example

C

L4

Flow Rate Q = 1,0 m3/s

Velocity C = 10 m/s

Height By = 0,2 m

Radius R0 = 0,8 m

We assume Cu to be constant along R0.

At q=90o, Q is reduced by 25%

L1

q

L3

R0

R

L2

By

Example

C

L4

Flow Rate Q = 0,75 m3/s

Velocity Cu = 12,9 m/s

Height By = 0,2 m

Radius R0 = 0,8 m

L1

q

L3

R0

R

L2

By

Example

C

L4

Flow Rate Q = 0,75 m3/s

Velocity Cu = 12,9 m/s

Height By = 0,2 m

Radius R0 = 0,8 m

L1

q

L3

R0

R

L2

L2 = 0,35 m

L3 = 0,22 m

L4 = 0,10 m

By

B

R0

Find the meridonial velocity from continuity:

k1 is a factor that reduce the inlet area due to the stay vanes

Spiral casing design procedure
• We know the flow rate, Q.
• Choose a velocity at the upstream section of the spiral casing, C
• Calculate the cross section at the inlet of the spiral casing:
• Calculate the velocity Cu at the radius Ro by using the equation:
Spiral casing design procedure
• Move 20o downstream the spiral casing and calculate the flow rate:
• Calculate the new spiral casing radius, r by iteration with the equation:
Design of the stay vanes
• The stay vanes have the main purpose of keeping the spiral casing together
• Dimensions have to be given due to the stresses in the stay vane
• The vanes are designed so that the flow is not disturbed by them
Flow induced pressure oscillation

Where

f = frequency [Hz]

B = relative frequency to the Von Karman oscillation

c = velocity of the water [m/s]

t = thickness of the stay vane [m]

Where

A = relative amplitude to the Von Karman oscillation

B = relative frequency to the Von Karman oscillation