Patent Application
20110271654
The subject matter disclosed herein related generally to gas turbine systems, and more particularly to diffusers in gas turbine systems.
Gas turbine systems are widely utilized in fields such as power generation. A conventional gas turbine system includes a compressor section, a combustor section, and at least one turbine section. The compressor section is configured to compress air as the air flows through the compressor section. The air is then flowed from the compressor section to the combustor section, where it is mixed with fuel and combusted, generating a hot gas flow. The hot gas flow is provided to the turbine section, which utilizes the hot gas flow by extracting energy from it to power the compressor, an electrical generator, and other various loads.
In conventional gas turbine systems, the air flow compressed in the compressor section is discharged from the compressor section at a relatively high velocity. The velocity of this air flow generally should be reduced to a velocity that is optimal for entering the combustor section. Thus, typical known compressor sections include an axial diffuser 19, as shown in
The utilization of typical known diffusers in gas turbine systems can subject the gas turbine system to a variety of problems. For example, known diffusers typically diffuse the air flow as the air flow travels along a generally longitudinal axis 90 of the gas turbine system. However, the air flow exiting the compressor section generally has an “exit swirl” component, meaning that the air flow is traveling in a generally rotational direction, with tangential and radial flow components, along with traveling in a generally longitudinal direction. To reduce this exit swirl before the air flow enters the axial diffuser 19, a guide vane or guide vanes 28 are typically disposed upstream of the axial diffuser 19 in the compressor section. The guide vanes 28 are designed to reduce the exit swirl. However, significant air flow pressure drops are associated with the use of guide vanes 28 to reduce the exit swirl, which results in losses in the performance and efficiency of the gas turbine system. Further, after the air flow exits a typical axial diffuser 19, the air flow must change direction multiple times as it flows to the combustor section, as shown in
Thus, a diffuser that reduces air flow pressure drops would be desired in the art. Additionally, a diffuser that utilizes the exit swirl associated with the air flow to guide the air flow to the combustor section would be advantageous. Further, a diffuser that eliminates the need for guide vanes in the compressor section would be desired.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one embodiment, a diffuser for a gas turbine system having a longitudinal axis is disclosed. The diffuser includes a plurality of diffuser ducts. Each of the plurality of diffuser ducts is disposed annularly about the longitudinal axis and has an inlet, an outlet, and a passage extending between the inlet and the outlet. The outlet of each of the plurality of diffuser ducts is tangentially offset from the inlet of the respective diffuser duct. Each of the plurality of diffuser ducts is configured to flow a gas flow therethrough, reducing the gas flow velocity.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. 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 various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with 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.
The compressor section 12 may compress a gas flow 80 as the gas flow 80 flows through the compressor section 12. The gas flow 80 may be, for example, air or any other suitable gas. The compressor section 12 may then flow the gas flow 80 to the combustor section 14, which may be configured to accept the gas flow 80, as discussed below.
As the gas flow 80 flows through the compressor section 12 after being compressed, it may flow in a generally longitudinal direction with respect to the longitudinal axis 90. However, the gas flow 80 may generally further include other flow components. For example, the gas flow 80 after being compressed may have flow components known collectively in the art as an “exit swirl.” Thus, the gas flow 80 may flow in a generally tangential direction, and may further flow in a generally radial direction.
In various embodiments, the compressor section 12 may include at least one guide vane 28. The guide vane 28 may reduce the exit swirl, thus reducing the tangential and radial flow components of the gas flow 80. In exemplary embodiments of the present disclosure, however, the compressor section 12 may be free from guide vanes 28.
As shown in
As mentioned above, the diffuser 20 of the present disclosure includes a plurality of diffuser ducts 30. As shown in
Further, the passage 34 may be generally tapered between the inlet 32 and the outlet 36. For example, in an exemplary embodiment, the passage 34 may be generally conically shaped. Alternatively, however, the passage 34 may have a generally rectangular cross-section, triangular cross-section, or any other suitable polygonal cross-section. It should be understood that the cross-sectional shape of the passage 34 may change throughout the passage 34 as the passage 34 tapers from the relatively smaller inlet 32 to the relatively larger outlet 36.
The diffuser ducts 30 may be disposed in an annular array about the longitudinal axis 90. Thus, as gas flow 80 flows in a generally longitudinal direction through the compressor section 12 and into the diffuser 20 after being compressed, the gas flow 80 may flow through the inlets 32 into the annular array of diffuser ducts 30.
The outlet 36 of each of the plurality of diffuser ducts 30 may be offset from the inlet 32 of the respective diffuser duct 30. The term “offset”, as used herein, means spaced from along the identified coordinate direction. For example, the outlet 36 of each of the plurality of diffuser ducts 30 may be tangentially offset from the inlet 32 of the respective diffuser duct 30, such as offset along a tangential axis 92. Because the outlet 36 of each of the plurality of diffuser ducts 30 is tangentially offset from the inlet 32 of the respective diffuser duct 30, the diffuser ducts 30 may advantageously utilize the tangential component of the gas flow 80 exit swirl to flow the gas flow 80 through the diffuser duets 30. In exemplary embodiments, this utilization of the tangential gas flow 80 component may eliminate the need for guide vanes 28 in the compressor section 12. Further, the utilization of the tangential gas flow 80 component may prevent gas flow 80 pressure losses due to flow direction changes in typical prior art gas turbine systems as the gas flow 80 flows from the compressor section 12 through the diffuser 20 to the combustor section 14.
Additionally, in some exemplary embodiments, the outlet 36 of each of the plurality of diffuser ducts 30 may be longitudinally offset from the inlet 32 of the respective diffuser duct 30, such as offset along the longitudinal axis 90. Because the outlet 36 of each of the plurality of diffuser ducts 30 is longitudinally offset from the inlet 32 of the respective diffuser duct 30, the diffuser ducts 30 may advantageously utilize the longitudinal component of the gas flow 80 to flow the gas flow 80 through the diffuser ducts 30.
Further, in some exemplary embodiments, the outlet 36 of each of the plurality of diffuser ducts 30 may be radially offset from the inlet 32 of the respective diffuser duct 30, such as offset along a radial axis 94. Because the outlet 36 of each of the plurality of diffuser ducts 30 is radially offset from the inlet 32 of the respective diffuser duct 30, the diffuser ducts 30 may advantageously utilize the radial component of the gas flow 80 exit swirl to flow the gas flow 80 through the diffuser ducts 30.
It should be understood that the tangential axis 92 and the radial axis 94 are defined individually for each diffuser duct 30 with respect to the circumference defined by the diffuser 20 and diffuser ducts 30, as shown in
Each of the passages 34 may include a first guide portion 40, as shown in
After gas flow 80 passes through the first guide portion 40 of the passage 34 of a diffuser duct 30, the gas flow 80 may continue to flow through the passage 34 towards the outlet 36. In certain exemplary embodiments, the passages 34 may extend in a generally linear manner downstream of the guide portion 40 with respect to the gas flow 80, as shown in
Each of the passages 34 may further include a second guide portion 42. In exemplary embodiments, the second guide portion 42 may be disposed adjacent the outlet 36 of the respective diffuser duct 30. Alternatively, however, the second guide portion 42 may be any portion of the passage 34 of the diffuser duct 30. The second guide portion 42 may be another portion of the passage 34 that further redirects the general direction of gas flow 80 within a diffuser duct 30. For example, the second guide portions 42 may be configured to guide the gas flow 80 from a generally tangential flow direction to a generally longitudinal flow direction. Alternatively, the second guide portions 42 may be configured to guide the gas flow 80 from a generally radial flow direction, a generally tangential and radial flow direction, a generally tangential and longitudinal flow direction, or a generally tangential, radial, and longitudinal flow direction to a generally longitudinal flow direction. It should be understood that gas flow 80 in any general direction, such as in a generally longitudinal direction, may have other flow components, such as radial and tangential flow components, and is not limited to flow strictly in the referenced direction.
It should be understood that before gas flow 80 passes through the second guide portion 42 of the passage 34 of a diffuser duct 30, the gas flow 80 may flow through the passage 34 towards the guide portion 42 and the outlet 36. In certain exemplary embodiments, the passages 34 may extend in a generally linear manner upstream of the second guide portion 42 with respect to the gas flow 80, as shown in
After the gas flow 80 flows through the outlet 36 of a diffuser duct 30 of the present disclosure, the gas flow 80 may exit the diffuser 20. In some exemplary embodiments, the gas flow 80 may exit the diffuser 20 flowing in a generally tangential direction. It should be understood, however, that the gas flow 80 may have radial and longitudinal flow components, and is not limited to flow in a strictly tangential direction. Alternatively, the gas flow 80 may exit the diffuser 20 flowing in a generally longitudinal direction. It should be understood, however, that the gas flow 80 may have tangential and radial flow components, and is not limited to flow in a strictly longitudinal direction. Further, the gas flow 80 may exit the diffuser 20 flowing in a generally radial direction. It should be understood, however, that the gas flow 80 may have tangential and longitudinal flow components, and is not limited to flow in a strictly radial direction.
As discussed above, after the gas flow 80 exits the diffuser 20 and the compressor section 12, the gas flow 80 may enter a plenum 22, or may directly enter the combustor section 14. For example, each of the diffuser ducts 30 may be coupled to a combustor can 24, and the gas flow 80 exiting each diffuser duct 30 may enter the combustor can 24 coupled with the diffuser duct 30. Thus, in exemplary embodiments, the diffuser 20 may include a number of diffuser ducts 20 equal to the number of combustor cans 24 in the combustor 14. For example, the diffuser 20, in various embodiments, may include 8, 12, or 16 diffuser ducts 30, or any other suitable number of diffuser ducts 30.
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 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.
