Patent Application
20150240667
This invention relates generally to integrating heat recovery steam generation (HRSG) systems with gas turbine exhaust components, and more specifically, to a turbine exhaust gas plenum designed to promote uniform flow of combustion gases into the HRSG.
In combined cycle power generation systems, heated exhaust gas discharged from gas turbines may be used by HRSG systems as a source of heat which may be transferred to a water source to generate superheated steam. In turn, the superheated steam may be used within steam turbines as a source of power. The heated exhaust gas from a gas turbine may be delivered to the HRSG system through, among other things, an exhaust plenum and diffuser, which may help convert the kinetic energy of the heated exhaust gas exiting the last stage of the gas turbine into potential energy in the form of increased static pressure. Once delivered to the HRSG system, the heated exhaust gas may traverse a series of heat exchanger elements, such as superheaters, re-heaters, evaporators, economizers, and so forth. The heat exchanger elements may be used to transfer heat from the heated exhaust gas to the water source to generate superheated steam. It is a design objective to promote uniform flow through the exhaust gas plenum without negatively impacting diffuser performance, i.e., enabling flow diffusion without appreciable total pressure loss.
In one embodiment, there is provided an exhaust gas diffuser for a turbomachine comprising a diffuser supported in a turbine rotor, aligned with an axis of the turbine rotor, the diffuser configured to re-direct turbine exhaust gas substantially ninety degrees from a first direction of flow along the axis; a plenum chamber in fluid communication with and surrounding an outlet end of the diffuser, the plenum chamber in fluid communication with a transition duct adapted to supply the exhaust gas to another turbomachine; wherein the plenum chamber expands in volume in a direction toward the transition duct.
In another embodiment, there is provided a turbomachine comprising a gas turbine section including a turbine rotor; a radial diffuser disposed along a first axis of the turbine rotor; an exhaust plenum comprising an inlet receiving a portion of the radial diffuser, the exhaust plenum extending along a second axis substantially perpendicular to the first axis, the plenum chamber expanding in volume along the second axis.
In still another embodiment, there is provided a combined cycle system comprising: a gas turbine including a turbine rotor extending along a first axis; a heat recovery steam generator; a steam turbine adapted to receive steam from the heat recovery steam generator; a radial diffuser disposed along the first axis; and an exhaust plenum comprising an inlet receiving a portion of the radial diffuser, the exhaust plenum extending along a second axis substantially perpendicular to the first axis, the plenum chamber expanding in volume along the second axis and communicating with the heat recovery steam generator.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters are not exclusive of other parameters of the disclosed embodiments.
The system 10 may also include a multi-stage HRSG 32. The simplified depiction of the HRSG 32 and its components are not intended to be limiting. Rather, the illustrated HRSG 32 is shown to convey the general arrangement of such systems. Heated exhaust gas 34 from the gas turbine 12 may be transported into the HRSG 32 and used to heat steam used to power the steam turbine 22. Exhaust from the low-pressure section 26 of the steam turbine 22 may be directed into a condenser 36. Condensate from the condenser 36 may, in turn, be directed into a low-pressure section of the HRSG 32 with the aid of a condensate pump 38.
The condensate may then flow through a low-pressure economizer 40 (LPECON), which is a device configured to heat feedwater with gases, may be used to heat the condensate. From the low-pressure economizer 40, the condensate may either be directed into a low-pressure evaporator 42 (LPEVAP) or to an intermediate-pressure economizer 44 (IPECON). Steam from the low-pressure evaporator 42 may be returned to the low-pressure section 26 of the steam turbine 22. Likewise, from the intermediate-pressure economizer 44, the condensate may either be directed into an intermediate-pressure evaporator 46 (IPEVAP) or to a high-pressure economizer 48 (HPECON). In addition, steam from the intermediate-pressure economizer 44 may be sent to a fuel gas heater (not shown) where the steam may be used to heat fuel gas for use in the combustor 18 of the gas turbine 12. Steam from the intermediate-pressure evaporator 46 may be sent to the intermediate-pressure section 28 of the steam turbine 22.
Finally, condensate from the high-pressure economizer 48 may be directed into a high-pressure evaporator 50 (HPEVAP). Steam exiting the high-pressure evaporator 50 may be directed into a primary high-pressure superheater 52 and a finishing high-pressure superheater 54, where the steam is superheated and eventually sent to the high-pressure section 30 of the steam turbine 22. Exhaust from the high-pressure section 30 of the steam turbine 22 may, in turn, be directed into the intermediate-pressure section 28 of the steam turbine 22, and exhaust from the intermediate-pressure section 28 of the steam turbine 22 may be directed into the low-pressure section 26 of the steam turbine 22.
An inter-stage attemperator 56 may be located in between the primary high-pressure superheater 52 and the finishing high-pressure superheater 54. The inter-stage attemperator 56 may allow for more robust control of the exhaust temperature of steam from the finishing high-pressure superheater 54.
In addition, exhaust from the high-pressure section 30 of the steam turbine 22 may be directed into a primary re-heater 58 and a secondary re-heater 60 where it may be re-heated before being directed into the intermediate-pressure section 28 of the steam turbine 22. The primary re-heater 58 and secondary re-heater 60 may also be associated with an inter-stage attemperator 62 for controlling the exhaust steam temperature from the re-heaters.
In combined cycle systems such as system 10, hot exhaust may flow from the gas turbine 12 and pass through the HRSG 32 and may be used to generate high-pressure, high-temperature steam. The steam produced by the HRSG 32 may then be passed through the steam turbine 22 for power generation. In addition, the produced steam may also be supplied to any other processes where superheated steam may be used. The gas turbine 12 generation cycle is often referred to as the “topping cycle,” whereas the steam turbine 22 generation cycle is often referred to as the “bottoming cycle.” By combining these two cycles as illustrated in
Therefore, one aspect of the combined cycle power generation system 10 is the ability to recapture heat from the heated exhaust gas 34 using the HRSG 32. As illustrated in
A more detailed illustration of how the gas turbine 12 functions may help illustrate how the heated exhaust gas 34 may be transferred to the HRSG 32 from the gas turbine 12. Accordingly,
Another aspect of certain components of the exhaust diffuser 68, in addition to directing the heated exhaust gas 34 to the HRSG 32, may be to ensure that certain aerodynamic properties of the heated exhaust gas 34 are achieved. For instance, an exhaust frame strut 72, illustrated in
The plenum 74 in the known configuration shown in
It will be understood that the internal vane components of the diffuser may be similar to the arrangement shown in
Significantly, the upstream and downstream side walls 108 and 110 are not parallel. As best seen in
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.
