Method and system for controlling gas turbine performance with a variable backflow margin

Patent metadata

Field	Value
Publication number	US-9366194-B2
Application number	US-201314018668-A
Country	US
Kind code	B2
Filing date	Sep 5, 2013
Priority date	Sep 5, 2013
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

A system and method for controlling the performance of a gas turbine system is provided. A backflow margin pressure ratio for a component is determined. A modified backflow margin pressure ratio for the component is calculated based on the number of fired hours and starts. Bleed air along a first flow path is controlled based on the modified backflow margin pressure ratio.

First claim

What is claimed:

1. A method for controlling a gas turbine having a compressor, a combustor and a turbine, the method comprising:
determining a backflow margin pressure ratio for a component of the turbine;
determining a modified backflow margin pressure ratio for the component based on a number of fired hours and starts;
selectively extracting a stream of bleed air from a stage of the compressor;
flowing at least a portion of the stream of bleed air through a first flow path from the compressor towards the component; and
controlling the stream of bleed air along the first flow path to selectively control an air pressure at a cavity of the component based on the modified backflow margin pressure ratio,
wherein determining a modified backflow margin pressure ratio comprises:
determining a backflow margin pressure ratio for the component;
determining a scalar; and
determining a modified backflow margin pressure ratio comprising a product of the scalar and the backflow margin pressure ratio.

2. The method of claim 1 wherein the scalar is a function of fired hours and starts.

3. The method of claim 1 , wherein the scalar is derived from life analysis of the component, based on applicable failure modes and probability of occurrence of the failure modes.

4. The method of claim 1 , wherein controlling the stream of bleed air comprises:
estimating a hot flow path gas pressure for the component;
determining a desired outer side wall cavity pressure to maintain the modified backflow margin pressure ratio for the hot flow path gas pressure; and
modulating the stream of bleed air to provide the stream of bleed air at the desired outer side wall cavity pressure.

5. The method of claim 1 , wherein the scalar accounts for a probability of failure occurring in a life cycle of the component.

6. The method of claim 1 , wherein the scalar has a value of 1 when the component is at an end of its life cycle.

7. The method of claim 1 further comprising:
determining a second modified backflow margin pressure ratio for a second component;
selectively extracting a second stream of bleed air from a second stage of the compressor;
flowing at least a portion of the stream of bleed air through a second flow path from the compressor towards the second component; and
controlling flow along the second flow path to selectively control an air pressure at the second component of the turbine based on the second modified backflow margin pressure ratio.

8. A system comprising:
a compressor;
a combustor;
a turbine; and
a subsystem comprising:
a subsystem that calculates a hot flow gas path pressure for a turbine component having a predetermined life cycle;
a subsystem that determines a backflow margin pressure ratio for the turbine component;
a subsystem that determines a scalar as a function of fired hours and starts;
a subsystem that determines a modified backflow margin pressure ratio by multiplying the scalar with the backflow margin pressure ratio for the turbine component;
a subsystem that extracts a stream of bleed air from a stage of the compressor; and
a subsystem that controls the stream of bleed air to provide a component cavity pressure based on the modified backflow margin pressure ratio.

9. The system of claim 8 , wherein the subsystem that determines a scalar comprises a subsystem that determines a scalar for the turbine component derived from life analysis of the turbine component based on applicable failure modes and probability of occurrence of the failure modes.

10. The system of claim 8 , wherein the scalar accounts for a probability of failure occurring during the predetermined life cycle of the turbine component.

11. The system of claim 8 , further comprising:
a load driven by the turbine;
an air inlet system coupled to the compressor; and
a distributed plant control system.

12. The system of claim 8 , further comprising:
a subsystem that selectively extracts a second stream of bleed air from a second stage of the compressor;
a subsystem that flows at least a portion of the second stream of bleed air through a second flow path from the compressor towards a second component of the turbine;
a subsystem that determines a second modified backflow margin pressure ratio for the second component; and
a subsystem that controls a flow along the second flow path to selectively control an air pressure at a cavity of the second component based on the second modified backflow margin pressure ratio.

13. A method for providing air from a compressor to at least one turbine component having a predetermined life cycle, the method comprising:
selectively extracting a stream of bleed air from the compressor;
flowing the stream of bleed air to the at least one turbine component; and
controlling the stream of bleed air flowing to the at least one turbine component according to an operating condition calculated from a modified backflow margin pressure ratio, wherein the modified backflow margin pressure ratio is a product of a scalar and a backflow margin pressure ratio for the at least one turbine component.

14. The method of claim 13 , wherein the scalar is derived from a life analysis of the at least one turbine component.

15. The method of claim 13 , wherein the scalar accounts for a probability of failure occurring during the predetermined life cycle of the at least one turbine component.

16. The method of claim 13 , further comprising flowing a second stream of bleed air from the compressor to a second component and controlling the second stream of bleed air according to an operating condition calculated from a second modified backflow margin pressure ratio for the second component.

17. The method of claim 16 , wherein the second modified backflow margin pressure ratio is a product of a second scalar and a second backflow margin for the second component.

18. The method of claim 17 , wherein the second scalar is derived from a life analysis of the second component.

Assignees

• Gen Electric

Inventors

• Feigl Markus
• Itzel Gary Michael

Classifications

• F02C9/18 Primary

  by bleeding, bypassing or acting on variable working fluid interconnections between turbines or compressors or their stages {(F02C3/113 takes precedence)} · CPC title

• F02C7/18

  the medium being gaseous, e.g. air {(F02C7/125 takes precedence)} · CPC title

• F02C6/08

  the gas being bled from the gas-turbine compressor · CPC title