EXHAUST TEMPERATURE BASED MODE CONTROL METHOD FOR GAS TURBINE AND GAS TURBINE

• US 20130042624A1
• Filed: 11/19/2010
• Published: 02/21/2013
• Est. Priority Date: 11/27/2009
• Status: Active Grant

• Current Assignee: Nuovo Pignone Tecnologie SRL (Nuovo Pignone International SRL)
• Original Assignee: Nuovo Pignone SPA (Nuovo Pignone International SRL)
• Inventors: Botarelli, Claudio
• Granted Patent: US 8,820,089 B2
• Time in Patent Office: Days
• US Class Current: 60/772
• CPC Class Codes: F02C 9/00 Controlling gas-turbine plants; Controlling fuel supply in air- breathing jet-propulsion plants controlling air intakes F02C7/057; controlling turbines F01D; controlling compressors F04D27/00; controlling in general G05
• CPC Class Codes: F02C 9/34 Joint control of separate flows to main and auxiliary burners
• CPC Class Codes: F05D 2270/301 Pressure
• CPC Class Codes: F05D 2270/303 Temperature
• CPC Class Codes: F23N 2221/00 Pretreatment or prehandling
• CPC Class Codes: F23N 2237/08 two or more different types of fuel simultaneously
• CPC Class Codes: F23N 2241/20 Gas turbines
• CPC Class Codes: F23N 5/003 using detectors sensitive to combustion gas properties F23N5/02, F23N5/18 - F23N5/26 take precedence
• CPC Class Codes: F23R 2900/00002 Gas turbine combustors adapted for fuels having low heating value [LHV]
• CPC Class Codes: F23R 3/36 Supply of different fuels

Abstract

Gas turbine, computer readable medium, and method for controlling an operating point of the gas turbine that includes a compressor, a combustor and a turbine is provided. The method includes determining a turbine pressure ratio, calculating a primary to lean-lean mode transfer threshold reference curve as a function of the turbine pressure ratio, determining at a first time when an exhaust temperature associated with the operating point is higher than an exhaust temperature of the primary to lean-lean mode transfer threshold reference curve for the same turbine pressure ratio, and changing, after a predetermined time after the first time, a split fuel quantity from a first value to a second value if the exhaust temperature associated with the operating point remains higher than the exhaust temperature of the primary to lean-lean mode transfer threshold reference curve.

Claims

1. A method for controlling an operating point of a gas turbine that includes a compressor, a combustor and at least a turbine, the method comprising:

determining an exhaust pressure drop at an exhaust of the turbine;

measuring a compressor pressure discharge at the compressor;

determining a turbine pressure ratio based on the exhaust pressure drop and the compressor pressure discharge;

calculating a primary to lean-lean mode transfer threshold reference curve as a function of the turbine pressure ratio, wherein the primary to lean-lean mode transfer threshold curve includes points at which an operation of the gas turbine is changed between a primary mode and a lean-lean mode;

determining at a first time when an exhaust temperature associated with the operating point is higher than an exhaust temperature of the primary to lean-lean mode transfer threshold reference curve for the same turbine pressure ratio; and

after a predetermined time after the first time, changing a split fuel quantity from a first value to a second value if the exhaust temperature associated with the operating point remains higher than the exhaust temperature of the primary to lean-lean mode transfer threshold reference curve,

wherein the primary mode is defined as providing more than half of the fuel to primary burners and providing a remaining or no fuel to a secondary burner of the combustor and also igniting the provided fuel in a primary region of the combustor, the primary region being adjacent to a secondary region,

wherein the lean-lean mode is defined as providing fuel to both the primary burners and the secondary burner and burning the provided fuel both in the primary region and the secondary region, and

wherein the split fuel quantity describes in percentages a first amount of the total fuel that is received by the primary burner and a second amount of the total fuel that is received by the secondary burners.

2. The method of claim 1, wherein the second value of the split fuel quantity is smaller than the first value, the primary mode is characterized by the first value, and the lean-lean pre-fill mode is characterized by the second value, which is part of the lean-lean mode.

3. The method of claim 2, further comprising:

changing, at a predetermined second time, the second value of the split fuel quantity to a third value, by which a lean-lean transient mode is characterized, which is part of the lean-lean mode.

4. The method of claim 3, further comprising:

changing, at a predetermined third time, the third value of the split fuel quantity to a fourth value, by which a lean-lean steady state mode is characterized, which is part of the lean-lean mode.

5. The method of claim 4, wherein the third value of the split fuel quantity is lower than the second value and wherein the fourth value is between the second value and the third value.

6. The method of claim 4, further comprising:

prior to operating the gas turbine, calculating lasting time intervals for a lean-lean pre-fill mode and the lean-lean transient mode while the lean-lean steady state mode has no precalculated lasting time interval.

7. The method of claim 4, further comprising:

determining at a fifth time that the exhaust temperature associated with the operating point is lower than a difference between (i) the exhaust temperature of the primary to lean-lean mode transfer threshold reference curve and (ii) a predetermined exhaust temperature value, both of which are taken for the same turbine pressure ratio; and

changing the split fuel quantity from the fourth value to the first value.

8. The method of claim 4, further comprising:

aborting the lean-lean transient mode and the lean-lean steady mode at any time at which the exhaust temperature associated with the operating point is lower than a difference between (i) the exhaust temperature of the primary to lean-lean mode transfer threshold reference curve and (ii) a predetermined exhaust temperature value, both of which are taken for the same turbine pressure ratio.

9. The method of claim 1, wherein calculating the primary to lean-lean mode transfer threshold reference curve comprises:

using a parameter indicative of a characteristic of the fuel to determine the primary to lean-lean mode transfer threshold reference curve, wherein the parameter is one of a lower heating value of the fuel, a NOx factor of the fuel, an upper to lower flammability ratio of the fuel, or a combination thereof.

10. A controller for controlling an operating point of a gas turbine that includes a compressor, a combustor and at least a turbine, the controller comprising:

a pressure sensor configured to measure a compressor pressure discharge at the compressor; and

a processor connected to the pressure sensor and configured to,

determine an exhaust pressure drop at an exhaust of the turbine,

determine a turbine pressure ratio based on the exhaust pressure drop and the compressor pressure discharge,

calculate a primary to lean-lean mode transfer threshold reference curve as a function of the turbine pressure ratio, wherein the primary to lean-lean mode transfer threshold curve includes points at which an operation of the gas turbine is changed between a primary mode and a lean-lean mode,

determine at a first time when an exhaust temperature associated with the operating point is higher than an exhaust temperature of the primary to lean-lean mode transfer threshold reference curve for the same turbine pressure ratio, and

after a predetermined time after the first time, change a split fuel quantity from a first value to a second value if the exhaust temperature associated with the operating point remains higher than the exhaust temperature of the primary to lean-lean mode transfer threshold reference curve,

wherein the primary mode is defined as providing more than half of the fuel to primary burners and providing a remaining or no fuel to a secondary burner of the combustor and also igniting the provided fuel in a primary region of the combustor, the primary region being adjacent to a secondary region,

wherein the lean-lean mode is defined as providing fuel to both the primary burners and the secondary burner and burning the provided fuel both in the primary region and the secondary region, and

wherein the split fuel quantity describes in percentages a first amount of the total fuel that is received by the primary burner and a second amount of the total fuel that is received by the secondary burners.