Patent Application
20130276450
The present invention relates to a gas turbine combustor geometry with a specific fuel and oxidizer flow arrangement that provides high combustion efficiency for stoichiometric diffusion combustion in gas turbine applications operating with oxygen-deficient working fluids.
Gas turbine applications utilizing low oxygen working fluids are known. Examples of such applications are carbon capture, oxyfuel, and high exhaust gas recirculation, all of which require high combustion efficiency to be economically viable. However, achieving such high combustion efficiency has not been attainable to date.
A need exists for high efficiency combustion in gas turbine applications where a low oxygen working fluid is used. The present invention seeks to satisfy that need.
In one aspect, the invention provides a combustor comprising a housing having an inner surface, an interior volume, and a nozzle and a liner assembly positioned within the housing. The liner is provided with at least one liner mixing hole and at least one liner dilution hole. The liner assembly is spaced apart from the inner surface of the housing to define a path extending longitudinally along the combustor between the liner assembly and the inner surface of the housing for transporting working fluid to the interior volume through the liner mixing and dilution holes. The liner mixing and dilution holes are axially positioned in the liner assembly at specific positions as a function of the diameter of the liner.
The combustor of the invention provides a stable flame and high combustion efficiency while ensuring adequate hardware durability. Since the applications of carbon capture, oxyfuel, and high exhaust gas recirculation require near stoichiometric combustion, the combustor of the present invention provides high efficiency combustion to ensure combustion is completed before fuel and oxidizers are diluted with the gas turbine working fluid.
The combustor of the invention thus provides a cost effective solution in gas turbine applications where a low oxygen working fluid is used to achieve improved combustion efficiency as compared to that obtained using conventional combustors.
Referring to the drawings,
The nozzle structure employed in the present invention is described in detail in commonly assigned US 2009/0223227, filed Mar. 5, 2008 (herein incorporated by reference).
The cooling holes 44,46,48 are positioned at different axial locations and are designed to accommodate, for example, about 30-32% of the GT working fluid at compressor discharge (i.e., the exit station of the compressor and starting station of the combustor). The size and number of cooling holes at any particular location is based on the desired effective heat transfer at that location.
Crown hole 28 accommodates about 6-9% of the GT working fluid at compressor discharge. The crown hole 28 creates a recirculation bubble 50 of length L2 of 0.65-1.05D where D is the internal diameter of the liner 10. This provides for higher combustion efficiency.
The dilution holes 40,42 are situated at an axial distance L3 of 1.3-1.7 D, where D is the internal diameter of the liner. The dilution holes create a jet penetration of L4 which is 1.4-1.6 times D2, where D2 is the diameter of the dilution hole. Strong shear mixing occurs between the oxidizer and fuel resulting in rapid reaction with a short residence time promoting a larger reaction zone. In addition, the mixing with the GT working fluid helps in controlling the peak flame temperature while keeping the flame away from the nozzle. The dilution holes accommodate 8-11% of the total combustor flow.
The center passage 24 of the nozzle is generally used for oxidizer flow, such as air, oxygen, diluted oxygen or fuel. The outer passages 22,26 are intended for gas turbine (GT) working fluid (typically a diluent rich fluid). The passages 22, 24, 26 are typically inclined such that they produce counter-rotating flow between the oxidizer and GT working fluid. This is illustrated in
The center passage 24 of the nozzle 14 typically contains angled fuel injection holes with an angle range from 40-60 degrees to produce high swirling flow. The center annular passage 24 of the nozzle is intended for gaseous fuel flow and is typically inclined with a cone angle of 20-26 degrees and a swirl angle of 5-16 degrees to the nozzle axis to induce counter-clockwise swirling (see
The center passage 24 of the nozzle is designed to flow a blended fluid containing 20-80% of the oxidizer and 80-20% of the GT working fluid at compressor discharge. The blending is optimized to control the reaction rates, and flame temperature to lower the dissociation loss from the reaction zone. The outer passage 26 is designed to flow 25-30% of the total combustor flow. This flow arrangement acts to delay the combustion reaction downstream of the nozzle and thereby avoid potential risk of hardware damage.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
