Bài giảng Thiết kế tuabin pelton

Design of Pelton
turbines

When to use a Pelton
turbine

Energy conversion in a
Pelton turbine
Outlet
Outlet of
the runner
Inlet of
the runner
Outlet of
the needle
Inlet of
the needle
2
2
c

Main dimensions for the
Pelton runner


The ideal Pelton runner
Absolute velocity from nozzle:
n1
Hg2c
⋅⋅=

1
Hg2
c
c
n
1
1
=
⋅⋅
=
Circumferential speed:
n
u1
1
Hg2
2
1
2
c
u
⋅⋅⋅==
5.0u
1
=
Euler`s turbine equation:
)cucu(2
u22u11h
⋅−⋅=η
1)05,00.15,0(2)(2
2211

=⋅−⋅⋅=⋅−⋅⋅=
uuh
cucu
η
1c
u1
=
0c
2u
=

The real Pelton runner
• For a real Pelton runner there will always be losses.
We will therefore set the hydraulic efficiency to:
96.0
h
=η
The absolute velocity from the nozzle will be:
995.0c99.0
u1
<≤
C
1u
can be set to 1,0 when dimensioning the turbine.
This gives us:
)cucu(2
u22u11h
⋅−⋅=η
⇓
48,0

0,12
96,0
c2
u
u1
n
1
=
⋅
=
⋅
η
=

From continuity equation:
u1
2
s
c
4
d
zQ
⋅
⋅π
⋅=
⇓
u1
s
cz
Q4

d
⋅π⋅
⋅
=
Where:
Z = number of nozzles
Q = flow rate
C
1u
=
n
Hg2
⋅⋅

The size of the bucket
and number of nozzles
4.3
d
B
1.3
s
≥>
Rules of thumb:
B = 3,1 · d
s
1 nozzle
B = 3,2 · d
s
2 nozzles
B = 3,3 · d

s
4-5 nozzles
B > 3,3 · d
s
6 nozzles

Number of buckets
17
≥
z
empirical

Number of buckets