Patent Application
20130291543
The invention relates to a combustor assembly for a gas turbine and, more particularly, to a DLN combustor assembly including an acoustics resonator.
Gas turbine systems typically include at least one gas turbine engine having a compressor, a combustor assembly, and a turbine. The combustor assembly may use dry, low NOx (DLN) combustion. In DLN combustion, fuel and air are pre-mixed prior to ignition, which lowers emissions. However, the lean pre-mixed combustion process is susceptible to flow disturbances and acoustic pressure waves. More particularly, flow disturbances and acoustic pressure waves could result in self-sustained pressure oscillations at various frequencies. These pressure oscillations may be referred to as combustion dynamics. Combustion dynamics can cause structural vibrations, wearing, and other performance degradations.
It is desirable to suppress combustion dynamics in a DLN combustor below specified levels to maintain low emissions. For axial mode frequencies, which are typically below 500 Hz, combustion dynamics can be effectively controlled using acoustic resonators provided at optimal locations.
In an exemplary embodiment, a gas turbine combustor assembly includes a casing defining an external boundary of the combustor assembly, and a plurality fuel nozzles disposed in the casing and coupled with a fuel supply. A liner receives fuel and air from the fuel nozzles and defines a combustion zone, and a flow sleeve is disposed between the liner and the casing. The flow sleeve serves to distribute compressor discharge air to a head end of the combustor assembly and to cool the liner. A transition piece is coupled with the liner and delivers products of combustion to a turbine. A resonator is disposed adjacent the flow sleeve upstream of the transition piece. The resonator serves to attenuate combustion dynamics.
In another exemplary embodiment, a system includes a compressor that compresses incoming airflow, a combustor assembly mixing the compressed incoming airflow with fuel and combusting the air and fuel mixture in a combustion zone, and a turbine receiving products of combustion from the combustor. The combustor assembly includes the noted casing, fuel nozzles, liner, flow sleeve, transition piece and resonator.
In yet another exemplary embodiment, a system includes a compressor that compresses incoming airflow, and a combustor assembly mixing the compressed incoming airflow with fuel and combusting the air and fuel mixture in a combustion zone. The combustor assembly includes a hot side downstream of the combustion zone and a cold side upstream of the combustion zone. The system also includes a turbine receiving products of combustion from the combustor. The combustor assembly includes a resonator positioned in the cold side of the combustor assembly in an annular passage between a flow sleeve and a casing of the combustor assembly.
As described above, gas turbine systems include combustor assemblies which may use a DLN or other combustion process that is susceptible to flow disturbances and/or acoustic pressure waves. Specifically, the combustion dynamics of the combustor assembly can result in self-sustained pressure oscillations that may cause structural vibrations, wearing, mechanical fatigue, thermal fatigue, and other performance degradations in the combustor assembly. One technique to mitigate combustion dynamics is the use of a resonator, such as a Helmholtz resonator. Specifically, a Helmholtz resonator is a damping mechanism that includes several narrow tubes, necks, or other passages connected to a large volume. The resonator operates to attenuate and absorb the combustion tones produced by the combustor assembly. The depth of the necks or passages and the size of the large volume enclosed by the resonator may be related to the frequency of the acoustic waves for which the resonator is effective.
The combustor assemblies 14 illustrated in
In an embodiment of the turbine system 10, compressor blades are included as components of the compressor 12. The blades within the compressor 12 are also coupled to the shaft 26, and will rotate as the shaft 26 is driven to rotate by the turbine 16, as described above. The rotation of the blades within the compressor 12 compresses air from an air intake 32 into pressurized air 34. The pressurized air 34 is then fed into the fuel nozzles 18 of the combustor assemblies 14. The fuel nozzles 18 mix the pressurized air 34 and fuel to produce a suitable mixture ratio for combustion (e.g., a combustion that causes the fuel to more completely burn) so as not to waste fuel or cause excess emissions.
In certain embodiments, the head end 54 includes plates 61 and 62 that may support the fuel nozzles 20 depicted in
The combustor assembly 14 also includes the resonator 40 disposed between the flow sleeve 60 and the casing 59 adjacent an inlet of the flow sleeve 60. As described above, the combustion process produces a variety of pressure waves, acoustic waves, and other oscillations referred to as combustion dynamics. Combustion dynamics may cause performance degradation, structural stresses, and mechanical or thermal fatigue in the combustor assembly 14. Therefore, combustor assemblies 14 may include the resonator 40, e.g., a Helmholtz resonator, to help mitigate the effects of combustion dynamics in the combustor assembly 14.
As shown in
In
The resonator 40 on the flow sleeve 60 can be tuned for a targeted frequency range. Additionally, since the resonator 40 may be secured to the flow sleeve 60, it is easily replaced.
The resonator of the described embodiments serves to suppress/attenuate combustion-generated acoustics. As a consequence, operability and durability of a DLN combustor can be extended.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
