201
6.4 The Single Impulse Stage or Laval Stage
direction, positive in the through-flow sense; y-axis in tangential direction, positive in the running sense; z-axis in radial direction positive away from the shaft. A
machine with positive blade speed is left-running:
Ω
Ω
= − 1 x . Flow is usually visualised top-down with axial machines. We follow this convention.
6.4.2 Work and Energy Relations
The primary relations are ( dq = 0, dU = 0):
Energy: dW dh
dv
dh
= +
=
1
2
2
0 ,
Work:
,
2
irr
1
1
dW
dp d v dq
2
r
=
+
+
Rotor work (Euler):
∆W u v
v
u
u
=
−
(
) .
2
1
Through velocity triangles it follows
Fig. 6.6 Velocity triangles with impulse turbines ( R s = 0, ψ = 1.95; work coefficient for optimum
efficiency with loss of outlet kinetic energy)
6.4 The Single Impulse Stage or Laval Stage
direction, positive in the through-flow sense; y-axis in tangential direction, positive in the running sense; z-axis in radial direction positive away from the shaft. A
machine with positive blade speed is left-running:
Ω
Ω
= − 1 x . Flow is usually visualised top-down with axial machines. We follow this convention.
6.4.2 Work and Energy Relations
The primary relations are ( dq = 0, dU = 0):
Energy: dW dh
dv
dh
= +
=
1
2
2
0 ,
Work:
,
2
irr
1
1
dW
dp d v dq
2
r
=
+
+
Rotor work (Euler):
∆W u v
v
u
u
=
−
(
) .
2
1
Through velocity triangles it follows
Fig. 6.6 Velocity triangles with impulse turbines ( R s = 0, ψ = 1.95; work coefficient for optimum
efficiency with loss of outlet kinetic energy)