Axial flow turbine having a diaphragm split in two halves at a horizontal joint plane
An axial flow turbine comprising a casing, a rotor having an axial rotational axis and rotatably mounted into the casing, at least one set of a plurality of moving blades supported by the rotor; and at least one diaphragm having an outer ring, an inner ring, concentric to the outer ring, and a plurality of static blades mounted therebetween, at least the outer ring being split in an upper half and a lower half along a vertical joint plane. The turbine diaphragm comprises an assembly system for assembling the upper half to the lower half while allowing the upper half and the lower half to move axially relative to each other.
1. An axial flow turbine comprising:
a casing,
a rotor having a rotational axis (Z) and rotatably mounted into said casing,
at least one set of a plurality of moving blades supported by said rotor; and
at least one diaphragm having an outer ring, an inner ring, concentric to the outer ring, and a plurality of static blades mounted therebetween, at least said at least one diaphragm being split in an upper half and a lower half along a horizontal joint plane, the upper half and the lower half having opposed joint surfaces,
wherein said at least one diaphragm comprises an assembly system for assembling the diaphragm upper half to the diaphragm lower half while allowing the diaphragm upper half and the diaphragm lower half to move axially relative to each other, while the opposed, joint surfaces are engaged.
2. A turbine according to claim 1 , wherein the assembly system comprises a guiding element for axially guiding the diaphragm upper half and the diaphragm lower half, and at least one fastening element for fastening the diaphragm upper and diaphragm lower halves together while allowing a relative axial movement of the diaphragm upper and diaphragm lower halves relative to each other, said fastening element being perpendicular to the horizontal joint plane.
3. A turbine according to claim 2 , wherein the at least one fastening element comprises a screw head, a smooth shrank portion and a threaded portion.
4. A turbine according to claim 3 , wherein the diaphragm upper half comprises a drilling made along a vertical axis, and having a diameter larger than the diameter of the shrank smooth portion.
5. A turbine according to claim 4 , wherein the diaphragm lower half comprises a threaded bolt hole coaxial with the drilling of the upper half and adapted to receive the threaded portion of the fastening element.
6. A turbine according to claim 3 , wherein the assembly system comprises a spacing element provided underneath the screw head of the fastening element.
7. A turbine according to claim 2 , wherein the guiding element of the assembly system comprises a feather key rigidly tightened to the upper half by two screws and an axial groove on a joint surface of the lower half to receive said feather key an axial clearance between each side of the feather key and each axial edge of said axial groove allowing the feather key to slide inside said axial groove.
8. A turbine according to claim 2 , wherein the guiding element of the assembly system comprises at least one cylinder positioned in an axial drilling in both the diaphragm upper and diaphragm lower halves of the at least one diaphragm, the outer diameter of the at least one cylinder being smaller than the inner diameter of the axial drilling.
9. A turbine according to claim 8 , wherein a clearance is between the screw head and the diaphragm upper half.