High efficiency stator for the second phase of a gas turbine

• US 20050247045A1
• Filed: 04/07/2005
• Published: 11/10/2005
• Est. Priority Date: 04/09/2004
• Status: Active Grant

• Current Assignee: Nuovo Pignone SPA (Nuovo Pignone International SRL)
• Original Assignee: Nuovo Pignone SPA (Nuovo Pignone International SRL)
• Inventors: Francini, Stefano
• Granted Patent: US 7,390,165 B2
• Time in Patent Office: Days
• US Class Current: 60/233
• CPC Class Codes: F01D 9/041 using blades F01D5/148 takes precedence
• CPC Class Codes: Y10S 416/02 Formulas of curves

Abstract

Stator for the second phase of a low-pressure turbine having a series of blades (1) each defined by coordinates of a discreet combination of points, in a Cartesian reference system (X,Y,Z), wherein the axis (Z) is a radial axis intersecting the central axis of the turbine.

The profile of each blade (1) is identified by means of a series of closed intersection curves (20) between the profile itself and planes (X,Y) lying at distances (Z) from the central axis.

Each blade (1) has an average throat angle defined by the cosine arc of the ratio between the average throat length at mid-height of the blade and the circumferential pitch evaluated at the radius of the average throat point; the average throat angle ranges from 57.8° to 60.8°.

Claims

1. A stator for the second phase of a low-pressure turbine having a series of blades each defined by coordinates of a discreet combination of points, in a Cartesian reference system (X,Y,Z), wherein the axis (Z) is a radial axis intersecting the central axis of the turbine, the profile of each blade being identified by means of a series of closed intersection curves between the profile itself and planes (X,Y) lying at distances (Z) from the central axis, each blade having an average throat angle defined by the cosine arc of the ratio between the average throat length at mid-height of the blade and the circumferential pitch evaluated at the radius of the average throat point, characterized in that the average throat angle ranges from 57.8°

to 60.8°

.

2. The stator for the second phase of a low-pressure turbine according to claim 1, characterized in that said average throat angle is 59.3°

.

3. The stator for the second phase of a low-pressure turbine according to claim 1, characterized in that each closed curve has a throat angle defined by the cosine arc of the ratio between the throat length and the circumferential pitch, evaluated at the radius corresponding to the distance (Z) from the central axis of the closed curve itself, and characterized in that each blade has a distribution of throat angles along the height (Z) of the blade, said distribution with respect to said average throat angle having a shift ranging from +1.5°

to −

1.5°

.

4. The stator for the second phase of a low-pressure turbine according to claim 1, characterized in that said closed curves are defined according to Table I, whose values refer to a room temperature profile and are divided by the value, expressed in millimeters, of the axial chord referring to the most external distance (Z) of the blade.

5. The stator for the second phase of a low-pressure turbine according to claim 1, characterized in that the profile of each blade has a tolerance of +/−

0.3 mm in a normal direction with respect to the profile of the blade itself.

6. The stator for the second phase of a low-pressure turbine according claim 1, characterized in that the profile of each blade comprises an anti-wear coating.

7. The stator for the second phase of a low-pressure turbine according to claim 6, characterized in that said coating has a thickness ranging from 0 to 0.5 mm.