Abstract: The present invention discloses a novel way of controlling a gas turbine engine to reduce emissions levels when demand for power from the gas turbine engine is reduced. The operating system provides a series of operating modes for a gas turbine combustor through which fuel is staged to gradually increase engine power, yet harmful emissions, such as carbon monoxide are kept within acceptable levels.

Abstract: The present invention discloses a novel and improved device and method for securing a combustion liner within a gas turbine combustor. The improved configuration comprises a plurality of equally spaced support tab assemblies secured about the combustion liner and positioned radially outward of the combustion zone. The support tab assemblies comprise parallel liner tabs which provide increased flexibility, greater structural support, and lower operating stresses.

Abstract: The present invention discloses a novel apparatus and way for reducing the recirculation zone at the inlet end of a combustor. The recirculation zone is reduced by altering the geometry of the inlet end through a tapering of the liner wall thickness and a tapering of the thermal barrier coating to reduce the bluff body effect at the combustion liner inlet end.

Abstract: A method for tuning a combustor of a gas turbine engine based on one or more monitored operating conditions is provided. One or more operating conditions of the gas turbine engine are monitored. The monitored operating conditions may include, for example, a low frequency tone, a high frequency tone, and a ratio of the low frequency tone to the high frequency tone. It is determined whether the ratio of the low frequency tone to the high frequency tone is within a first predefined normal range. If the ratio of the low frequency tone to the high frequency tone is within the first predefined normal range, a determination is made not to tune the gas turbine engine. But, if the ratio of the low frequency tone to the high frequency tone is not within the first predefined normal range, a determination is made to tune the gas turbine engine.

Abstract: Methods are provided for ensuring non-excessive variation of a gradient of an applied split bias versus firing temperature of a gas turbine engine. It is determined that an incremental split bias step is to be taken, and a current firing temperature of the gas turbine engine is identified on a graph. A first difference between a split schedule and an applied schedule gradient is calculated using lower firing temperatures than the current firing temperature, and a second difference is calculated using higher firing temperatures. If the first difference exceeds a predetermined limit, the incremental split bias step is not allowed at a lower firing temperature, and similarly, if the second difference exceeds a predetermined limit, the incremental split bias step is not allowed at a higher firing temperature.

Abstract: Methods and systems are provided for automatically tuning a combustor of a gas turbine engine during a transient period, such as when a state of the gas turbine engine is changing. Once it has been determined whether the state of the gas turbine engine is changing, it is then determined whether a lean blowout is imminent, which is based conditions being monitored. A stability bias is applied to the system if either the state is changing or if lean blowout is imminent until the lean blowout is no longer determined to be imminent. The stability bias monitors operating conditions of the gas turbine engine and determines when one of the operating conditions has overcome a threshold value. Once a threshold value is overcome, a fuel flow fraction is adjusted by a predefined increment. The application of the stability bias is gradually terminated once it is determined that the lean blowout is no longer imminent.

Abstract: A tuning process is provided for dynamically tuning a gas-turbine (GT) engine to correct for flashback events without directly measuring occurrences of the flashback events at the GT engine. Initially, readings are taken that measure low-frequency dynamics at the GT engine. A determination of whether flashback criteria are met by an instantaneous signal that quantifies a detected spike within the measured low-frequency dynamics is carried out, where the flashback criteria include the following: identifying the spike overcomes a multiple of an average of the low-frequency dynamics measured over a predefined period of time; and identifying the spike overcomes a preestablished minimum amplitude. Upon the spike meeting the flashback criteria, a count is added to a running record of spikes, which is compared to an alarm limit. If the alarm limit is triggered, action(s) are invoked to address the flashback events, such as adjusting fuel-flow splits of the GT engine.

Abstract: A tuning process is provided for monitoring fuel properties of a fuel being consumed by a gas turbine (GT) engine, and for dynamically tuning the GT engine as a function of changes to the monitored fuel properties. Initially, readings are taken from the GT engine during a reference calibration, or commissioning, and utilized to calculate an initial-pressure-drop reference value. The tuning process during commercial operation takes post-calibration readings from the GT engine to calculate a fuel property parameter, which represents a heating value of the fuel. Specifically, the fuel property parameter is calculated by deriving a corrected-pressure-drop dynamic value as a function of pressure and temperature readings of the fuel at a point upstream of a combustor and pressure drops across fuel nozzles that introduce the fuel into the combustor, and solving a ratio of the dynamic value and the reference value.

Abstract: The present invention discloses a novel apparatus and way for controlling a velocity of a fuel-air mixture entering a gas turbine combustion system. The apparatus comprises a hemispherical dome assembly which directs a fuel-air mixture along a portion of the outer wall of a combustion liner and turns the fuel-air mixture to enter the combustion liner in a manner coaxial to the combustor axis and radially outward of a pilot fuel nozzle so as to regulate the velocity of the fuel-air mixture.

Abstract: The present invention discloses a novel apparatus and method for a mixing fuel and air in a gas turbine combustion system. The mixer helps to mix fuel and air while being able to selectively increase the fuel flow to a shear to a shear layer of a pilot flame in order to reduce polluting emissions. The mixer directs a flow of air radially inward into the combustion system and includes two sets of fuel injectors within each radially-oriented vane. A first plurality of fuel injectors operate independent of a second plurality of fuel injectors and the second plurality of fuel injectors are positioned to selectively modulate the fuel flow to the shear layer of the resulting pilot flame.

Abstract: The present invention discloses a novel apparatus and method for operating a gas turbine combustor having a structural configuration proximate a pilot region of the combustor which seeks to minimize the onset of thermo acoustic dynamics. The pilot region of the combustor includes a generally cylindrical extension having an outlet end with an irregular profile which incorporates asymmetries into the system so as to destroy any coherent structures.

Abstract: The present invention is directed to a mounting system for a gas turbine transition duct. The mounting system includes a generally C-shaped mounting bracket having a generally radially extending first portion, an arc-shaped second portion, and a generally radially extending third portion. Each of the first portion and third portion includes a spherical bearing and the second portion has a plurality of sets of mounting holes. In another embodiment of the present invention, a gas turbine transition duct is provided having a panel assembly, an aft frame secured to the panel assembly and a mounting system for securing the transition duct to a turbine inlet. The panel assembly includes two formed sheets of metal secured together along axial seams. The panel assembly is secured to an aft frame that is capable of expanding in the circumferential direction due to thermal growth.

Abstract: A combustor end cap assembly having an improved cooling configuration is disclosed. Embodiments of the present invention are directed towards an apparatus and method for cooling an effusion plate of the combustor end cap assembly. The combustor end cap assembly also incorporates an impingement plate having a plurality of cooling holes with the impingement plate positioned a predetermined distance from the effusion plate. The cooling fluid passes through the impingement plate and is directed towards and onto the effusion plate for cooling of the effusion plate.

Abstract: A transition duct having a thermally free aft frame and being capable of adjusting the natural frequency is disclosed. The aft frame is capable of permitting movement due to thermal gradients with the transition duct. The transition duct utilizes a spring plate located adjacent to an aft mounting bracket, where the spring plate, based on its thickness can either increase or decrease a frequency of the transition duct. Such an arrangement ensures that the transition duct natural frequency does not coincide with or cross other critical engine and/or combustor frequencies.

Abstract: Tuning processes implemented by an auto-tune controller are provided for measuring and adjusting the combustion dynamics and the emission composition of a gas turbine (GT) engine via a tuning process. Initially, the tuning process includes monitoring parameters, such as combustion dynamics and emission composition. Upon determining that one or more of the monitored parameters exceed a critical value, these “out-of-tune” parameters are compared to a scanning order table. Upon comparison, the first out-of-tune parameter that is matched within the scanning order table is addressed. The first out-of-tune parameter is then plotted as overlaid slopes on respective graphs, where the graph represents a fuel-flow split. Typically, the slopes are plotted as a particular out-of-tune parameter against a particular fuel-flow split. The slopes for each graph are considered together by taking into account the combined impact on each out-of-tune parameter when a fuel-flow split is selected for adjustment.

Abstract: A transition duct assembly with a thermally free aft frame and mounting system for use in a gas turbine engine are disclosed. The aft frame is capable of adjusting to thermal gradients while the mounting system provides for at least transverse movement of the transition duct during engine assembly. The mounting system also provides a means for raising the natural frequency of the transition duct outside of the engine's dynamic excitation ranges.

Abstract: Embodiments for minimizing relative thermal growth within a fuel nozzle of a gas turbine combustor are disclosed. Fuel nozzle configurations are provided in which a heating fluid is provided to one or more passages in a fuel nozzle from feed holes in the fuel nozzle base. The heating fluid passes through the fuel nozzle, thereby raising the operating temperature of portions of the fuel nozzle to reduce differences in thermal gradients within the fuel nozzle. Various fuel nozzle configurations and passageway geometries are also disclosed.

Abstract: Tuning processes implemented by an auto-tune controller are provided for measuring and adjusting the combustion dynamics and the emission composition of a gas turbine (GT) engine via a tuning process. Initially, the tuning process includes monitoring parameters, such as combustion dynamics and emission composition. Upon determining that one or more of the monitored parameters exceed a critical value, these “out-of-tune” parameters are compared to a scanning order table. Upon comparison, the first out-of-tune parameter that is matched within the scanning order table is addressed. The first out-of-tune parameter is then plotted as overlaid slopes on respective graphs, where the graph represents a fuel-flow split. Typically, the slopes are plotted as a particular out-of-tune parameter against a particular fuel-flow split. The slopes for each graph are considered together by taking into account the combined impact on each out-of-tune parameter when a fuel-flow split is selected for adjustment.

Abstract: A tuning process is provided for monitoring fuel properties of a fuel being consumed by a gas turbine (GT) engine, and for dynamically tuning the GT engine as a function of changes to the monitored fuel properties. Initially, readings are taken from the GT engine during a reference calibration, or commissioning, and utilized to calculate an initial-pressure-drop reference value. The tuning process during commercial operation takes post-calibration readings from the GT engine to calculate a fuel property parameter, which represents a heating value of the fuel. Specifically, the fuel property parameter is calculated by deriving a corrected-pressure-drop dynamic value as a function of pressure and temperature readings of the fuel at a point upstream of a combustor and pressure drops across fuel nozzles that introduce the fuel into the combustor, and solving a ratio of the dynamic value and the reference value.

Abstract: An auto-tune controller and tuning process implemented thereby for measuring and tuning the combustion dynamics and emissions of a GT engine, relative to predetermined upper limits, are provided. Initially, the tuning process includes monitoring the combustion dynamics of a plurality of combustors and emissions for a plurality of conditions. Upon determination that one or more of the conditions exceeds a predetermined upper limit, a fuel flow split to a fuel circuit on all of the combustors on the engine is adjusted by a predetermined amount. The control system continues to monitor the combustion dynamics and to recursively adjust the fuel flow split by the predetermined amount until the combustion dynamics and/or emissions are operating within a prescribed range of the GT engine.