Abstract:
In a turbomachine having an inlet, a compressor, and a turbine, a closed loop sends fluid from a stage of the compressor to a heat exchanger in the turbine and to the inlet. The closed loop heats the fluid, cools the turbine, and delivers heated fluid to the inlet. A mixer can be interposed between the heat exchanger and the inlet to mix fluid from the heat exchanger with compressor discharge fluid, delivering the mixed fluid to the inlet. The mixer can control flow received so that desired temperature and/or flow rate can be provided to the inlet.

Description:
BACKGROUND OF THE INVENTION 
     The disclosure relates generally to turbomachinery, and more particularly, to inlet bleed heating assemblies for turbomachinery, such as gas turbines, including turbomachinery installed in combined cycle power plants and other arrangements. 
     A turbomachine, such as a gas turbine and/or a combined cycle power plant, can be operated at a range of loads and/or power settings. However, typically a gas turbine will suffer degradation in efficiency when running at less than full load/power and/or when running lean. To reduce the degradation, inlet bleed heating (IBH) has been employed, in which a supply of compressor discharge air is fed into the inlet of the gas turbine during less-than-full load/power. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Embodiments of the invention disclosed herein may take the form of a turbomachine inlet with a first conduit configured for fluid communication with a stage of a compressor of a turbomachine and with a cavity located at a stage of a turbine of the turbomachine and substantially sealed against fluid communication with the stage of the turbine. A second conduit can be configured for fluid communication with the cavity and with an inlet of the turbomachine. 
     Another embodiment can include a turbomachine having an inlet, a compressor in fluid communication with the inlet and including at least one stage and a compressor discharge, and a turbine in fluid communication with the compressor discharge and including at least one stage. A first conduit can be in fluid communication with a stage of the compressor and a cavity at a stage of the turbine. A second conduit can be in fluid communication with the cavity at the stage of the turbine and with the inlet. 
     A further embodiment can include a turbomachine having an inlet, a compressor with at least one compressor stage and a compressor discharge, and a turbine with at least one turbine stage. The inlet, compressor, and turbine can be arranged in serial fluid communication so that fluid entering the inlet passes through the compressor into and through the turbine. In addition, the turbomachine can include an inlet bleed heater in fluid communication with a stage of the compressor, a heat exchanger at a stage of the turbine, and the inlet, the heat exchanger being substantially sealed from fluid communication with the stage of the turbine. 
     Other aspects of the invention provide methods of making embodiments of the invention disclosed herein, as well as variants of the apparatus, which include and/or implement some or all of the actions and/or features described herein. The illustrative aspects of the invention are designed to solve one or more of the problems herein described and/or one or more other problems not discussed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       These and other features of the disclosure will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various aspects of the invention. 
         FIG. 1  shows a schematic diagram of an example of a turbomachine including an inlet bleed heating assembly according to embodiments of the invention disclosed herein. 
         FIG. 2  shows a schematic elevation diagram of an example of a turbine with which an inlet bleed heating assembly according to embodiments of the invention disclosed herein can be used. 
         FIG. 3  shows a partial schematic cross sectional diagram of the turbine of  FIG. 2  taken along line  3 - 3  showing a heat exchanging cavity according to embodiments of the invention disclosed herein. 
         FIG. 4  shows a partial schematic cross sectional diagram of the turbine of  FIGS. 2 and 3  with examples of flow path altering elements added according to embodiments of the invention disclosed herein. 
         FIG. 5  shows a partial schematic cross sectional diagram of the turbine of  FIGS. 2 and 3  with examples of flow path altering elements added according to embodiments of the invention disclosed herein. 
         FIG. 6  shows a schematic graph comparing efficiency vs. load for a gas turbine employing embodiments of the invention and for a typical system. 
     
    
    
     It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings. 
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Broadly, embodiments of the invention herein can bleed fluid from a compressor stage, send it through a heat exchanger in a turbine, and use the heated fluid in inlet bleed heating. The heat exchanger can simultaneously heat the fluid and cool the turbine, enhancing operation of the turbine, and the heated fluid enhances operation of the compressor beyond conventional inlet bleed heating. The heat exchanger can be formed within an existing cavity in the turbine, such as by adding one or more walls in a gap between inner and outer casings of the turbine, and can be in fluid communication with cooling passages of turbine blades to enhance fluid heating and turbine cooling. A mixer can receive the heated fluid as well as a bleed from the compressor discharge, varying flow from each to produce a mixed flow of a desired temperature and/or flow rate that can be used or the inlet bleed heating. For example, a control system of the gas turbine can actuate a valve of the mixer to obtain a desired temperature/flow rate for inlet bleed heating. 
     With reference to  FIG. 1 , a turbomachine  1 , such as a gas turbine, can include a compressor  10  and a turbine  20 . Compressor  10  can include one or more inlets  11  leading to at least one compressor stage  12  and a compressor discharge  13 . Compressor  10  can include an inner casing  14  and an outer casing  15  separated by a gap or cavity  16  which, in embodiments, can be substantially annular and/or substantially frustroconical. Fluid passing through discharge  13  is fed to combustors (not shown) that drive turbine  20 , which drives compressor  10  via a shaft  17  or the like. Turbine  20  can include at least one turbine stage  22  surrounded by an inner casing  24  and an outer casing  25 . As with compressor  10 , a gap or cavity  26  can be formed between inner and outer casings  24 ,  25 . To improve efficiency, an inlet bleed heater  30  can be included to introduce heated fluid into compressor inlet  11 . 
     Embodiments of the invention disclosed herein can include an inlet bled heating assembly  100  including a first conduit  102  that can draw fluid from compressor  10 , such as from one or more stage(s)  12 , and send the fluid to a heat exchanging cavity  104  in gap or cavity  26  of turbine  20 . Heat exchanging cavity  104  can extend over one stage  22  or over a plurality of stages  22  as may be suitable and/or desired. A second conduit  106  can transfer fluid from heat exchanging cavity  104  to inlet bleed heater  30  and/or inlet  11 , though in embodiments second conduit  106  can transfer fluid to a mixer  108 . A third fluid conduit  110  can transfer fluid from another source, such as compressor discharge  13 , to mixer  108  so that fluid from second and third conduits  106 ,  110  can be mixed and sent through a fourth conduit  112  to inlet  11  and/or inlet bleed heater  30 , though in other embodiments, third conduit  110  can deliver fluid to inlet  11  and/or inlet bleed heater  30  directly. Thus, where third conduit  110  delivers fluid to mixer  108 , the mixed flow in fourth conduit  112  can be a contributor to inlet bleed heating in embodiments, and in other embodiments, fourth conduit  112  can deliver the mixed flow directly to inlet  11 , which can allow elimination of inlet bleed heater  30 . Mixer  108  in embodiments can include at least one valve or the like  114  with which flow from second and third conduits  106 ,  110  can be adjusted to achieve a desired temperature and/or flow rate of the mixed flow in fourth conduit  112 . In embodiments, valve(s)  114  can be operated or actuated by a controller  119 , such as a control system of turbomachine  1 , an inlet bleed heater controller, and/or a controller specific to inlet bleed heating assembly  100 , though in other embodiments, valve  114  can be operated or actuated manually. 
     Heat exchanging cavity  104  can be bounded by opposed end walls  116  that can extend between inner and outer casings  24 ,  25  substantially perpendicular to a longitudinal axis of turbine  20 . In addition, end walls  116  can extend circumferentially about inner casing  24 . As can be seen in  FIG. 2 , cavity  104  can additionally be bounded by one or more dividing walls  118  extending between inner and outer casings  24 ,  25  substantially parallel to the longitudinal axis of turbine  20 . A plurality of heat exchanging cavities  104  can thus be formed by using multiple dividing walls  118  and/or multiple pairs of opposed end walls  116 , each cavity  104  being in fluid communication with a respective first conduit  102  and second conduit  106 . Thus, fluid can enter a cavity  104  from a respective second conduit  102  via an inlet port or the like  120 , flow through cavity  104 , and exit to a respective third conduit  106  via an exit port or the like  122 . As should be clear, cavity  104  can include and/or be in fluid communication with cooling passages of turbine blades of a stage or stages  22  at which cavity  104  is located for enhanced cooling of turbine  20  and heating of fluid travelling through cavity  104 . 
     With particular reference to  FIG. 3 , a flow path through a heat exchanging cavity  104  is illustrated. In this example, multiple such heat exchanging cavities  104  are shown and bounded by dividing walls  118 . First conduit  102  can be in fluid communication with cavity  104  via inlet port  120  so that fluid can enter and flow through cavity  104  to exit port  122  and second conduit  106 . Turbine blades  27  may include a cooling arrangement, such as including a hollow portion and/or cooling passages, that can be in fluid communication with cavity  104 , if desired. Flow in this example is primarily through cavity  104  even when turbine blades  27  are in fluid communication with cavity  104 . Where greater flow into turbine blades  27  is desired, radial baffles  124  can be added at points in cavity  104 , as seen in  FIG. 4 . Radial baffles  124  can extend longitudinally and between inner and outer casings  24 ,  25  so that flow from first conduit  102  can be directed into a first turbine blade  27 , back to cavity  104 , into a next turbine blade  27 , back to cavity  104 , and so forth until the fluid exits to second conduit  106 . Alternatively, as seen in  FIG. 5 , a circumferential baffle  126  can be added substantially parallel to inner and outer casings  24 ,  25 , with radial baffles  124  extending between inner casing  24  and circumferential baffle  126 . Thus configured, a portion of flow entering cavity  104  can be directed into turbine blades  27 , while another portion can pass between baffle  126  and outer casing  25 . While examples are seen in  FIGS. 3-5 , any combination of radial and circumferential baffles  124 ,  126  can be employed as may be suitable and/or desired to achieve a flow rate and/or degree of heating of fluid flowing through conduits  102 ,  106  and/or to cool turbine  20  and/or turbine blades  27 . 
     By heating fluid in cavity  104  and introducing the heated fluid into inlet  11 , whether alone or in conjunction with additional heated fluid from inlet bleed heater  30 , performance at off-peak turbomachine operation levels can be improved. Further, by mixing and varying flow rates of fluid from cavity  104  and compressor discharge  13  with mixer  108  before introducing the fluid to inlet  11 , specific temperatures and/or flow rates can be achieved to further enhance turbomachine operation. For example, as seen in  FIG. 6 , by employing embodiments of the invention disclosed herein when a gas turbine is operated at less than maximum load, such as, for example, less than about 80% or lower of maximum load, an efficiency increase of from about 0.3% to about 0.5% can be achieved. Such improvements to turbomachine operation can thereby save fuel and/or wear on the turbomachine, and, in the case of turbomachines employing DLN combustors, desired emissions levels can still be achieved. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.