Claims
- 1. In a turbine moving blade assembly for a steam turbine which has a plurality of stages each provided with turbine moving blades attached to a turbine shaft and fixed turbine nozzle blades positioned axially adjacent the turbine moving blades, the turbine moving blades being circumferentially spaced with adjacent turbine moving blades being interconnected intermediate their ends and also at their radially outer tips, each of the turbine moving blades being twisted from the blade root to the blade tip, the improvement wherein the twist angles at blade cross-sections along the height of each turbine moving blade are differentially twisted to produce a distribution of throat•pitch ratio (S/T) along the turbine moving blade height direction from the blade root to the blade tip that follows a curve having at least one minimum and one maximum.
- 2. A turbine moving blade assembly according to claim 1, wherein said throat•pitch ratio (SIT) distribution is off-set to take into account turbine moving blade untwisting that occurs during operation of the steam turbine due to centrifugal force.
- 3. A turbine moving blade assembly according to claim 1 or claim 2, wherein the maximum is located in the turbine moving blade height range of about 15% to about 45%.
- 4. A turbine moving blade assembly according to claim 1 or claim 2, wherein the minimum is located in the turbine moving blade height range of about 70% to about 95%.
- 5. A turbine moving blade assembly according to claim 3, wherein the minimum is located in the turbine moving blade height range of about 70% to about 95%.
- 6. A turbine moving blade assembly according to claim 1 or claim 2, wherein the turbine moving blade assembly has a diameter of at least 1.4 m at the root, the turbine moving blade height is at least 1.0 m, and the turbine shaft rotates at 300 rpm or 3600 rpm.
- 7. A turbine moving blade assembly according to claim 1 or claim 2, wherein said turbine moving blades are made of a titanium alloy with a composition of about 88% to about 92% titanium, about 4% to about 8% aluminium and about 2% to about 6% vanadium by weight percent.
- 8. A turbine moving blade assembly according to claim 1 or claim 2, wherein the intermediate connections of the turbine moving blades are located within a turbine moving blade height range of about 50% to about 70%.
- 9. A turbine moving blade assembly according to claim 1, wherein the turbine moving blade differential twist angles are adopted in a final turbine stage and at least one turbine stage upstream of the final turbine.
- 10. In a steam turbine having a casing, a shaft rotatable in the casing and a plurality of stages each provided with turbine moving blades attached to the turbine shaft and fixed turbine nozzle blades positioned axially adjacent the turbine moving blades, the turbine moving blades being circumferentially spaced with adjacent turbine moving blades interconnected intermediate their ends and also at their radially outer tips, each of the turbine moving blades being twisted from the blade root to the blade tip, the improvement wherein the twist angles at blade cross-sections along the height of each turbine moving blade are differentially twisted to produce a distribution of throat•pitch ratio (S/T) along the turbine moving blade height direction from the blade root to the blade tip that follows a curve having at least one minimum and one maximum.
Priority Claims (1)
Number |
Date |
Country |
Kind |
H10-218262 |
Jul 1998 |
JP |
|
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser. No. 09/361,570, filed Jul. 27, 1999.
Continuations (1)
|
Number |
Date |
Country |
Parent |
09361570 |
Jul 1999 |
US |
Child |
10025597 |
Dec 2001 |
US |