Turbine assembly

1. A turbine assembly comprising:

a rotor with a rotational axis;

a casing enclosing the rotor to form a flow passage therebetween;

a first rotating blade row having a plurality of circumferentially adjacent first rotating blades each with a first shroud, at a first rotating blade end that is distal from the rotor and blade airfoils extending into the flow passage;

a first sealing means located between the casing and the first shroud;

a stationary vane row axially adjacent and downstream of the first rotating blade row, having a plurality of circumferentially adjacent stationary vanes each with a base member and a vane airfoil extending into the flow passage;

a second rotating blade row in the flow passage axially adjacent and downstream of the stationary vane row having a plurality of circumferentially adjacent second rotating blades each with a second shroud, at a second rotating blade end that is distal from the rotor; and

a second sealing means located between the casing and the second shroud,

wherein a first cavity is formed by the first shroud, the sealing means and the base member and a second cavity is formed by the second shroud, the base member and the second sealing means, and

a bypass-passage extending from a first end at the first cavity to a second end at the second cavity so as to bypass the flow passage and the vane airfoil.

2. The turbine assembly of claim 1 , wherein each of the vane airfoils has a leading edge wherein the first end of the bypass-passage is located at a point of the first cavity circumferentially between the leading edges of two of the circumferentially adjacent vanes airfoils.

3. The turbine assembly of claim 1 , wherein the bypass-passage is radially displaced from rotational axis.

4. The turbine assembly of claim 1 , wherein the bypass-passage is parallel to the rotational axis.

5. The turbine assembly of claim 1 , wherein the bypass-passage is angled from the rotational axis in a direction of a normal rotational direction of the rotor of between −30 degrees and 30 degrees.

6. The turbine assembly of claim 1 , wherein the bypass-passage is angled from the rotational axis in a direction of a normal rotational direction of the rotor between 0 degrees and 10 degrees.

7. The turbine assembly of claim 1 , wherein the first end of the bypass-passage has a larger cross sectional area that the second end of the bypass-passage.

8. The turbine assembly of claim 1 , wherein the bypass-passage includes at least one non-linear section.

9. The turbine assembly of claim 1 , further comprising a plurality of bypass-passages.

10. The turbine assembly of claim 1 , configured as a gas turbine.

11. The turbine assembly of claim 1 , wherein the base member is a vane root wherein the bypass-passage extends through the vane root.

12. The turbine assembly of claim 1 , configured as an impulse type steam turbine.

13. The turbine assembly of claim 12 , wherein the base member comprises a diaphragm configured and arranged as a support ring for the stationary vanes of the stationary vane row wherein bypass-passage extends through a steam turbine diaphragm.

14. The turbine assembly of claim 12 , wherein the base member comprises a diaphragm configured and arranged as a support ring for the stationary vanes of the stationary vane row wherein the bypass-passage extends around the diaphragm.

15. The turbine assembly of claim 13 , wherein the diaphragm includes:

a first extension ring extending between the first shroud and the casing wherein the first sealing means is mounted on the extension ring between the extension ring and the first shroud; and

a second extension ring extending between the second shroud and the casing wherein the second sealing means is mounted on the second extension ring between the second extension ring and the first shroud.