A gas turbine engine with a single stage combustor includes an external premixer to provide premixed fuel/compressed air to the combustor as well as compressed air for dilution; and an automatic controller to provide feedback control of the compressed air flow and fuel flow to the premixer in accord
A gas turbine engine with a single stage combustor includes an external premixer to provide premixed fuel/compressed air to the combustor as well as compressed air for dilution; and an automatic controller to provide feedback control of the compressed air flow and fuel flow to the premixer in accordance with actual power versus power demand. The fuel/compressed air mixture is combusted in a combustor and the combustion gases and dilution air are expanded in a turbine. The engine further includes a bleed valve under control of the controller for diverting sufficient compressed dilution air past the turbine to induce increased fuel flow and compressed air flow to the premixer for delivery to, and combustion of, the combustor to compensate for the power deficit due to the bled air, to provide selected minimum premixer exit velocities during engine operation.
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What is claimed is: 1. A gas turbine engine comprising an air compressor, a premixer for mixing fuel with a first portion of compressed air to provide a fuel/air mixture the premixer having a fixed area exit, a combustor for receiving and combusting the mixture to provide combustion gases, the comp
What is claimed is: 1. A gas turbine engine comprising an air compressor, a premixer for mixing fuel with a first portion of compressed air to provide a fuel/air mixture the premixer having a fixed area exit, a combustor for receiving and combusting the mixture to provide combustion gases, the compressor also providing a second portion of the compressed air to an exit of the combustor as dilution air, a compressed air valve for controlling the first compressed air portion, a fuel valve for controlling fuel flow to the premixer, and a turbine operatively connected to the combustor for expanding the combustion gases and the dilution air to drive the compressor and provide net power, the engine further comprising: (1) an engine controller responsive to engine power output and engine power demand for controlling the fuel valve and the air valve, wherein in response to a decrease in engine power output relative to engine power demand the controller will increase the fuel flow and air flow to the premixer, whereby the mixture flow velocity through the premixer exit will also increase, and (2) means for diverting part of the second portion of compressed air to bypass at least the turbine, and wherein the engine controller is also operatively connected to the diverting means for selectively controlling the bypass air flow to maintain at least a selected minimum mixture flow velocity through the premixer exit. 2. The engine as in claim 1, wherein the engine includes a cooling shroud defining in part a flow path for the second portion of compressed air, and wherein the engine controller also selectively controls the diverting means to divert a sufficient amount of compressed air past the combustor and the turbine to minimize buckling of the combustor. 3. The gas turbine engine as in claim 1, wherein the diverting means includes a bleed valve positioned in a compressed air flow path downstream of the compressor and upstream of the air valve. 4. The gas turbine engine as in claim 1, wherein the premixer has a fixed area exit. 5. The gas turbine engine as in claim 1, wherein the combustor is a single stage combustor. 6. The gas turbine as in claim 1 wherein the engine controller includes a microprocessor under program control to provide a mixture with a preselected fuel/air ratio. 7. A gas turbine engine including a compressor for providing compressed air; a premixer for providing a fuel/compressed air mixture; a combustor for combusting the fuel/air mixture; and a turbine for expanding the gases received from the combustor to provide power and driving at least the compressor, the engine further comprising: (a) a first compressed air flow path from the compressor to the premixer, for air to be mixed with fuel, the resultant fuel/air mixture being provided via a premixer exit to the combustor for producing combustion gases, the combustion gases being thereafter provided to the turbine for power producing expansion therein; (b) a second compressed air flow path from the compressor for air bypassing the premixer for admission to the combustor as dilution air for mixing with the combustion gases and for expansion in the turbine; (c) a bleed valve operatively connected in the second compressed air flow path to divert air past the turbine; (d) an air valve operatively connected in the first compressed air flow path; (e) a fuel valve for controlling fuel flow to the premixer; and (f) an engine controller responsive to engine power demand and operatively connected to control the fuel valve and the air valve to provide a preselected fuel/air ratio to the premixer, the controller also being operatively connected to control the bleed valve to divert sufficient compressed air to provide a selected minimum mixture velocity through the premixer exit. 8. The apparatus as in claim 7, wherein the premixer exit has a fixed area. 9. The apparatus as in claim 7, wherein the engine controller also selectively controls the bleed valve to divert a sufficient amount of dilution air to minimize buckling of the combustor. 10. A method of operating a gas turbine engine of the type having an air compressor driven by a turbine for supplying compressed air through an air valve to a premixer for mixing with fuel to provide a fuel/air mixture for delivery to a combustor through a premixer exit, for generating combustion gases, the compressor also supplying compressed air directly to the combustor as dilution air, the turbine extracting power from both the combustion gases and dilution air, the method comprising: controlling the fuel flow and compressed air flow to the premixer to provide a sufficient fuel/air mixture to the combustor to maintain a preselected power level; and diverting a portion of the dilution air past the turbine, whereby power cannot be extracted by the turbine from the diverted air portion, the diverting step thereby resulting in a power deficit, wherein the diverting step includes diverting sufficient dilution air such that a controlled increase in the flow of fuel and air to the premixer to make up the power deficit provides at least a selected minimum fuel/air mixture velocity through the premixer exit. 11. The method as in claim 10, wherein the diverting step is carried out only during operation below a preselected power level. 12. The method as in claim 11, wherein the preselected power level is about 25% or less. 13. The method as in claim 10, wherein method includes flowing the fuel/air mixture from the premixer to the combustor through a fixed area exit. 14. The method as in claim 10, wherein the diverting step is carried out step-wise during engine operation. 15. The method as in claim 10 wherein the diverting step is carried out automatically under the control of an engine controller. 16. The method as in claim 15 wherein automatic control is automatic feedback control based upon deviation between power demand and a sensed actual power output. 17. The method as in claim 14 wherein the bleed valve is step-wise variable and is controlled by the controller to provide one or more discrete bypass flow rates. 18. The method as in claim 10 wherein the controlling step and the diverting step are carried out by a microprocessor under program control. 19. The method as in claim 10, wherein the diverting step also includes diverting a sufficient amount of dilution air past the combustor and the turbine to minimize buckling of the combustor. 20. The method as in claim 10 further including the step of controlling the fuel flow and the compressed air flow to the premixer to provide a preselected fuel/air ratio.
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이 특허에 인용된 특허 (5)
Ikeda Hiraku (Katsuta JPX) Sasada Tetsuo (Hitachi JPX) Sato Isao (Hitachi JPX) Moritomo Yoshikazu (Hitachi JPX) Takahashi Koji (Hitachi JPX) Takaba Minoru (Hitachi JPX), Control apparatus and a control method of a gas turbine combustor.
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