Patent Application
20120208136
The present invention generally involves a system and method for operating a combustor. In particular embodiments, the systems and methods of the present invention may be used for operating a combustor in a gas turbine.
Combustors are commonly used to ignite fuel to produce combustion gases having a high temperature and pressure. For example, gas turbines typically include one or more combustors to generate power or thrust. A typical gas turbine used to generate electrical power includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Ambient air may be supplied to the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through one or more nozzles in each combustor where the compressed working fluid mixes with fuel and ignites to generate combustion gases having a high temperature, pressure, and velocity. The combustion gases expand in the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
The fuel supplied to the combustor may be a liquid fuel, a gaseous fuel, or a combination of liquid and gaseous fuels, depending on various factors such as the operating mode, operating level, and availability of various fuels. If the liquid fuel, gaseous fuel, and/or other fluids are not evenly mixed with the compressed working fluid prior to combustion, localized hot spots may form in the combustor, particularly near the nozzle exits. The localized hot spots may increase the production of nitrous oxides in the fuel rich regions, while the fuel lean regions may increase the production of carbon monoxide and unburned hydrocarbons, all of which are undesirable exhaust emissions. In addition, the fuel rich regions may increase the chance for the flame in the combustor to flash back into the nozzles and/or become attached inside the nozzles which may damage the nozzles. Although flame flash back and flame holding may occur with any fuel, they occur more readily with high reactive fuels, such as hydrogen, that have a higher burning rate, flame velocity, and wider flammability range.
The presence and location of the fuel rich regions and fuel lean regions may vary with the operating mode, operating level, and/or type of fuel being used, and a variety of systems and methods exist to allow higher operating combustor temperatures while minimizing undesirable emissions, flash back, and flame holding. For example, some systems and methods reduce undesirable emissions at lower operating levels by injecting atomizing air near the reduced flow of liquid fuel to enhance dispersion of the liquid fuel with the compressed working fluid prior to combustion. Other systems and methods reduce undesirable emissions and/or flame holding events at higher operating levels by injecting a diluent, such as water, steam, combustion exhaust gases, or an inert gas, near the increased flow of liquid and/or gaseous fuel to reduce the peak flame temperature in the combustor and/or cool the downstream surface of the nozzle. However, the various systems and methods often require specialized nozzle designs and typically have reduced effectiveness at reducing undesirable emissions and/or flame holding events across the entire range of combustor operating modes and levels. Therefore, a system and method for operating a combustor over a wide range of operating modes and levels to improve combustor efficiency, reduce undesirable emissions, and/or prevent flash back and flame holding events would be useful.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a system for operating a combustor. The system includes a nozzle, a fuel passage through the nozzle having a fuel inlet and a fuel outlet, and an air passage through the nozzle having an air inlet and an air outlet. A fuel supply is in fluid communication with the fuel inlet, and an air supply is in fluid communication with the air inlet and the fuel inlet.
Another embodiment of the present invention is system for operating a combustor that includes a nozzle, a fuel passage through the nozzle having a fuel inlet and a fuel outlet, a diluent passage through the nozzle having a diluent inlet and a diluent outlet, and an air passage through the nozzle having an air inlet and an air outlet. A fuel supply is in fluid communication with the fuel inlet, and an air supply is in fluid communication with the air inlet and the fuel inlet. A sensor provides a parameter signal reflective of an operating parameter of the combustor, and a controller connected to said sensor receives the parameter signal from the sensor and generates a control signal to at least one of the fuel supply or the air supply based on the parameter signal.
The present invention may also include a method for operating a combustor that includes flowing a fuel through a fuel inlet in a nozzle and flowing air through an air inlet in the nozzle. The method further includes sensing an operating parameter of the combustor, generating a signal reflective of the operating parameter, and controlling a flow of at least one of air or diluent to the fuel inlet based on the signal reflective of the operating parameter.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.
Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Various embodiments of the present invention include a system and method for operating a combustor. In particular embodiments, liquid and/or gas fuels may flow through a nozzle in the combustor, and a controller may adjust the fuel flow and/or the injection of a diluent and/or air into the fuel flow to enhance the efficiency of the combustor, reduce undesirable emissions, and/or prevent or reduce the occurrence or damaging effects of flash back and flame holding. Although described generally in the context of a combustor incorporated into a gas turbine, embodiments of the present invention may be applied to any combustor and are not limited to a gas turbine combustor unless specifically recited in the claims.
The nozzle 14 may also include a diluent passage 42 and/or an air passage 44 through the nozzle 14. The diluent passage 42 has a diluent inlet 46 and a diluent outlet 48 so that the diluent passage 42 provides fluid communication through the nozzle 14 and into the combustion chamber 22. Similarly, the air passage 44 has an air inlet 50 and an air outlet 52 so that the air passage 44 provides fluid communication through the nozzle 14 and into the combustion chamber 22. The diluent and air passages 42, 44 are generally located in the nozzles so that the respective diluent and air outlets 48, 52 are proximate to one or more fuel outlets 36, 40. For example, as shown in
The fuel supply 62, 64 is in fluid communication with the nozzle through the one or more fuel inlets (e.g., the gaseous and/or liquid fuel inlets 34, 38) and/or the diluent inlet 46. In this manner, the system 60 may support various fuel operating modes for the combustor 10 by supplying liquid fuel to the combustion chamber 22 through the liquid fuel inlet 38 and/or diluent inlet 46 and gaseous fuel to the combustion chamber 22 through the gaseous fuel inlet 34, the liquid fuel inlet 38, and/or the diluent inlet 46. For example, the combustor 10 may operate using only liquid fuel supplied through valve 70 to the liquid fuel passage 32 and/or through valves 72 and 74 to the diluent passage 42. If desired, a homogenizer 76 connected between the liquid fuel supply 64 and diluent supply 66 may be used to emulsify the liquid fuel and diluent prior to injection into the combustion chamber 22 through the liquid fuel passage 32 and/or the diluent passage 42. Alternately, the combustor 10 may also operate using a combination of liquid and gaseous fuel, with the liquid fuel supplied through valve 70 to the liquid fuel passage 32 and/or through valves 72 and 74 to the diluent passage 42, and the gaseous fuel supplied through valve 78 to the gaseous passage 30 and/or through valve 80 to the diluent passage 32. Lastly, the combustor 10 may operate using only gaseous fuel supplied through valve 78 to the gaseous fuel passage 30, through valve 80 to the liquid fuel passage 32, and/or through valve 82 to the diluent passage 44. As a result, the combustor 10 may operate with a staged supply of liquid and/or gaseous fuel simultaneously supplied through the liquid fuel passage 32, the diluent passage 42, and the gaseous fuel passage 30.
The diluent supply 66 is in fluid communication with the nozzle 14 through the diluent inlet 46, the one or more fuel inlets (e.g., the gaseous and/or liquid fuel inlets 34, 38), and/or the air inlet 50. Similarly, the air supply 68 is in fluid communication with the nozzle 14 through the air inlet 50, the one or more fuel inlets (e.g., the gaseous and/or liquid fuel inlets 34, 38), and/or the diluent inlet 46. In this manner, the diluent may be supplied through valve 84 to the diluent passage 42 and/or through valve 86 to the air passage 44, and the air may be supplied through valve 88 to the air passage 44 and/or through valve 90 to the diluent passage 42 for a number of purposes. For example, during reduced power or turndown operations, the air may be supplied through the air and/or diluent passages 44, 42 to inject air proximate to the liquid fuel outlet 40 to disperse or atomize the liquid fuel exiting the nozzle 14 to enhance mixing between the liquid fuel and the compressed working fluid prior to combustion. During higher power operations, and for some design considerations during lower power operations that benefit from adjustments to the fuel outlets, the diluent may be supplied through the diluent and/or air passages 42, 44 and/or the air may be supplied through the air and/or diluent passages 44, 42 to inject the diluent and/or air proximate to the liquid and/or gaseous fuel outlets 40, 36 to cool the downstream surface of the nozzle 14 and/or reduce the peak flame temperature of the combustion flame. Maintaining the desired temperature on the downstream surface of the nozzle 14 protects the nozzle 14 from excessive wear, premature failure, and/or carbon deposition (coking) on the surface of the nozzle 14. Reducing the peak flame temperature of the combustion flame reduces the production of undesirable emissions. Lastly, the diluent may be supplied through the diluent and/or air passages 42, 44 and/or the air may be supplied through the air and/or diluent passages 44, 42 to inject the diluent and/or air proximate to the liquid and/or gaseous fuel outlets 40, 36 in response to a flash back or flame holding event to cool the surface of the nozzle 14 and/or prevent or extinguish the flame holding.
As shown in
As shown in
The controller 110 may be operably connected to one or more sensors that generate one or more parameter signals reflective of operating parameters of the combustor 10. By way of illustration and not as a limitation of the invention, the sensors may be broadly organized as combustor/gas turbine performance sensors 114, fluid sensors 116, and stability sensors 118. The combustion/gas turbine sensors 114 may be located throughout the combustor 10 or gas turbine to provide real time or near real-time parameter signals 120 reflective of the operating parameters of the combustor 10 or gas turbine. For example, the combustion/gas turbine sensors 114 may monitor and provide parameter signals 120 reflective of the pressure of the compressed working fluid (compressor discharge pressure), temperature of the compressed working fluid, various temperatures inside the combustor 10, gas turbine exhaust temperature, power level, or any number of other operating parameters of the combustor 10 or gas turbine. The fluid sensors 116 may be positioned in various fluid supplies to the combustor 10 to provide parameter signals 122 reflective of the physical characteristics of the various fluids. For example, the fluid sensors 116 may monitor and provide parameter signals 122 reflective of the ambient air temperature and/or humidity, diluent temperature and/or pressure, or pressure, temperature, and/or calorie content of the fuel. The stability sensors 118 may similarly be positioned throughout the combustor 10 and/or gas turbine to provide parameter signals 124 reflective of abnormal conditions in the combustor 10 and/or gas turbine. For example, the stability sensors 118 may monitor and provide parameter signals 124 reflective of temperatures inside or proximate to each nozzle 14 to indicate a flashback or flame holding event, pressure amplitudes and/or frequencies inside the combustor 10 to indicate combustor flame stability, or emissions content to indicate excessive undesirable emissions.
As shown in block 132, the method may further include monitoring one or more operating parameters of the combustor 10 and generating one or more parameter signals reflective of the operating parameters. For example, combustor/gas turbine performance sensors 114 may generate parameter signals 120 reflective of the pressure of the compressed working fluid (compressor discharge pressure), temperature of the compressed working fluid, various temperatures inside the combustor 10, gas turbine exhaust temperature, power level, or any number of other operating parameters of the combustor 10 or gas turbine. The fluid sensors 116 may generate parameter signals 122 reflective of the ambient air temperature and/or humidity, diluent temperature and/or pressure, or pressure, temperature, and/or calorie content of the fuel. The stability sensors 118 may generate parameter signals 124 reflective of temperatures inside or proximate to each nozzle 114, pressure amplitudes and/or frequencies inside the combustor 10, or emissions content to indicate excessive undesirable emissions.
The controller 110 receives the one or more parameter signals 120, 122, 124 and/or the operating mode signal 126 and generates the control signal 112. At block 136, the control signal 112 adjusts the flow of at least one of the fuel, diluent, or air through the nozzle 14 to the combustor 10. For example, during normal operations, the controller 110 may simply adjust the flow rate of one or more of the fuel, diluent, or air through the respective fuel, diluent, or air passages in response to a change in power demand, ambient temperature, fuel quality, or various other operating parameters of the combustor 10 or gas turbine. Specifically, the control signal 112 from the controller 110 may adjust the fuel supply in response to the fluid sensor 116 parameter signal 122 to allow the combustor 10 to operate using multiple liquid and gaseous fuels having different heat values or Wobbe indices without adversely affecting the combustor flame stability, creating excessive pressure oscillations, and/or increasing the risk or occurrence of flame holding. In this manner, the system 60 may optimize fuel and/or diluent consumption to increase the combustor 10 efficiency and reduce operating costs. Alternately, or in addition, the control signal 112 from the controller 110 may adjust the flow rate of one or more of the fuel, diluent, or air through one or more of the cross connected fuel, diluent, or air passages in response to a change in the operating mode signal 126. For example, the control signal 112 from the controller 110 may adjust the diluent and/or air flow through the liquid fuel passage 32 to purge the liquid fuel from the liquid fuel passage 32 in anticipation of operating in a gaseous fuel only mode.
As another example, the control signal 112 from the controller 110 may adjust the flow rate of one or more of the fuel, diluent, or air through one or more of the cross connected fuel or diluent passages in response to the stability sensor 118 parameter signal 124. For example, the control signal 112 and the controller 110 may adjust the diluent and/or air flow through one or more of the fuel passages 30, 32 in response to a detected flame holding event and/or excessive amount of undesirable emissions.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other and examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
