Abstract:
A turbine stator vane with a closed loop sequential impingement cooling circuit with an impingement cooling insert that includes a three-pass serpentine flow cooling circuit, where each leg of the circuit includes a cooling air supply channel and a return channel with rows of impingement cooling holes and rows of return openings connecting them together. Turn channels are located at the outer diameter and the inner diameter of the vane to direct cooling air from the first leg and into the second and third legs in series. Impingement holes are formed on impingement surfaces that alternate with return slots formed in the insert.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit to U.S. Provisional Application 62/295,747 filed on Feb. 16, 2016 and entitled TURBINE STATOR VANE WITH MULTIPLE OD PRESSURE FEEDS and U.S. Provisional Application 62/296,920 filed on Feb. 18, 2016 and entitled TURBINE STATOR VANE WITH SPENT COOLING AIR RETURN. 
     
    
     GOVERNMENT LICENSE RIGHTS 
       [0002]    This invention was made with Government support under contract number DE-FE0023975 awarded by Department of Energy. The Government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    Field of the Invention 
         [0004]    The present invention relates generally to cooled turbine components and specifically to semi-closed-loop internally cooled turbine stator vanes that return spent cooling flow to the combustion process to enhance power output and thermodynamic efficiency. 
         [0005]    Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
         [0006]    The current state-of-the-art in gas turbine vane OD (Outer Diameter) multi-cooling feed is shown in the prior art U.S. Pat. No. 8,961,108 issued to Bergman et al. on Feb. 24, 2015. In this approach, the cooling system contains two cooling flow passageways through the mounting hook, that are not in fluid communication with each other, fed by the same first high pressure plenum. A second plenum supplies the aft cavities of the stator with an intermediate pressure. High pressure and intermediate pressure flows are extracted from the flow of the compressed air from the compressor located on the same centerline. As shown, the flow is provided through plenums at the BOAS (Blade Outer Air Seal) and the vane OD platform. The flow is then routed and split through the mounting hooks (passageways 1 &amp; 2, fed from plenum 1) and direct into the aft cooling passages for cooling flow passageway 3 (F3, fed from plenum 2). 
         [0007]    In this current state-of-the-art multi-feed cooling technique, the first plenum supplied by the compressor high pressure air feeds the first passage and second passages. The first passage supplies the compressor bleed high pressure cooling air to the adjacent BOAS. The second passage is routed through the mounting hook and supplies the same (first) plenum cooling air to the vane OD and the airfoil leading edge. The second plenum, supplied by the compressor from a higher stage (lower pressure) then feeds the third passage from the vane OD into the trailing edge cooling channels of the airfoil. The second passage cooling air then exits the leading edge through film holes and the third passage cooling air exits out the trailing edge to mix with the hot gas stream passing through the turbine. The mixing of spent cooling air with the hot gas stream results in performance and power losses to the machine. Higher pressure air also introduces leakages at the vane OD platform, which in this technique were reduced with the addition of multiple seals, shown in the Bergman patent U.S. Pat. No. 8,961,108. However, with high pressure or over-pressurized supply air, these seals can contribute to large leaks of the cooling air into the gas path. 
         [0008]    Introduction of over-pressurized cooling air recirculated through turbine stator vane would introduce a significant amount of leakage flow at the OD and ID (Inner Diameter) if used for cooling the surrounding hooks, pre-swirler or U-rings, downstream ring segments, and the back side of vane platforms. A second lower-pressure source is introduced and an updated configuration to fit multiple feed plumbing into the vane OD developed here to address this issue. 
         [0009]    In a gas turbine engine, the prior art gas turbine stator vane cooling shown in U.S. Pat. No. 5,383,766 issued to Przirembel on Jan. 24, 1995 shows cooling accomplished by extracting relatively cool air from the compressor and delivering it to the turbine to be used as coolant. While the remainder of the compressor discharge air continues to flow into the combustor, to be mixed with fuel and to be burned to provide the needed hot working fluid, which subsequently flows around the turbine vane airfoil, the cooling air is supplied separately to the vane cooling system. A plurality of impingement inserts are installed inside the vane airfoil. Cooling air is supplied to the inside of the inserts and is allowed to flow through a plurality of holes in the inserts to impinge upon the inside of the vane airfoil to create an enhanced (impingement) heat transfer effect. In this example, the cooling air which flows through the impingement insert  28  then flows through film cooling holes at the leading edge, and forward pressure and suction sides to further cool the part by convection heat transfer within the holes and also by creating a film cooling effect via a layer of cooler air that flows over the surface of the airfoil. Cooling air which entered impingement insert  30  is also discharged from film cooling holes located along the aft pressure side surface of the airfoil and also from the trailing edge cooling passages. 
         [0010]    In the prior art Przirembel cooling design, all of the cooling air is ejected from the airfoil and mixes with the hot gas which is flowing around the airfoil. Such mixing of spent cooling air results in performance and power losses to the engine. For example, the ability of the cooling air, whose pressure has been increased in the compressor, to provide useful work in the turbine is greatly reduced because no heat has been added to it in the combustor. Further, the ejection of spent cooling air into the primary hot gas flow reduces turbine efficiency via mixing losses because the cooling air, which enters the primary hot gas flow with relatively low velocity, slows the hot gases as the two streams intersect and achieve a balance of momentum. Finally, the power of the engine is reduced as the temperature of the hot gases are diluted with the cooler cooling air. 
         [0011]    In another prior art stator vane cooling design, a conventional open-loop air cooled turbine nozzle causes the hot gas temperature to be decreased by 280° F. (155° C.) as a result of the mixing of cold spent cooling air with the hot gases flowing around the airfoil. 
         [0012]    In another prior art cooling design, a closed-loop steam cooling system replaces the open loop air cooled system where a temperature reduction of the hot gas is reduced to 80° F. (44° C.). While this illustrates the potential benefit of closed loop cooling, this steam cooled system is rather complicated and has several technical challenges that are overcome by the present invention. To give a few examples: 1) heat rejected from the turbine vanes via the steam coolant is returned to a low energy point of the thermodynamic system, thereby limiting the efficiency and power output of the machine; 2) use of steam cooling requires a separate steam system to be implemented, maintained and controlled in an operational condition; 3) the adverse effects of steam on the metallurgy of the materials used to construct the turbine components must be overcome; and 4) any loss of steam through leaks must be replaced with makeup water that may be expensive or unavailable depending on the installation location. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    The present invention relates generally to cooled turbine components and specifically to turbine stator vanes fed with multiple pressures including recirculated cooling air pressurized over compressor exit, to reduce leakages while enhancing power output and thermodynamic efficiency. A higher pressure cooling air is passed through a stator vane in a closed loop cooling circuit in which the spent cooling air is then discharged into the combustor. The higher pressure cooling air is required to provide both cooling for the stator vane and have enough pressure to flow into the combustor. A lower pressure cooling air is used to provide cooling for the endwalls and hooks of the stator vane, where this spent cooling air is then discharged into the hot gas stream. 
         [0014]    A turbine stator vane with sequential impingement cooling and where spent cooling air is delivered to the combustor to be burned with fuel instead of discharged into the turbine hot gas path. The turbine stator vane is for use in a twin spool gas turbine engine in which the two spools are capable of operating independently and where a closed loop cooling circuit for both the rotor blades and the stator vanes are used in which all spent cooling air is passed into the combustor. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0015]      FIG. 1  shows a cross section top view of a closed loop cooling circuit for a turbine stator vane cooling circuit of the present invention 
           [0016]      FIG. 2  shows a cross section view of a stator vane in a turbine with the cooling air inlet and outlet connections of the cooling circuit of the present invention. 
           [0017]      FIG. 3  shows a top view of a vane doublet with the cooling circuit of the present invention. 
           [0018]      FIG. 4  shows a top view of a vane singlet with the cooling circuit of the present invention. 
           [0019]      FIG. 5  shows a combined cycle power plant with an industrial gas turbine engine of the present invention. 
           [0020]      FIG. 6  shows another embodiment combined cycle power plant with an industrial gas turbine engine of the present invention in which the turbine stator vane is cooled. 
           [0021]      FIG. 7  shows another embodiment combined cycle power plant with an industrial gas turbine engine of the present invention in which the turbine stator vane is cooled. 
           [0022]      FIG. 8  shows a turbine stator vane with two sequential impingement cooling inserts of the present invention. 
           [0023]      FIG. 9  shows the turbine stator vane of  FIG. 8  without the two sequential impingement cooling inserts. 
           [0024]      FIG. 10  shows the two sequential impingement cooling inserts from a suction side of the present invention. 
           [0025]      FIG. 11  shows a close-up view of a section of the forward sequential impingement insert with return openings of the present invention. 
           [0026]      FIG. 12  shows a close-up view of a section of the aft sequential impingement insert with return openings of the present invention. 
           [0027]      FIG. 13  shows the two sequential impingement cooling inserts of the present invention from the pressure side. 
           [0028]      FIG. 14  shows the two sequential impingement cooling inserts of the present invention from the pressure side. 
           [0029]      FIG. 15  shows the turbine stator vane outer endwall with a cover plate enclosing the two sequential impingement cooling inserts of the present invention. 
           [0030]      FIG. 16  shows the turbine stator vane inner endwall with a cover plate enclosing the two sequential impingement cooling inserts of the present invention. 
           [0031]      FIG. 17  shows the turbine stator vane without the two sequential impingement cooling inserts with the cooling air supply and discharge openings and coolant connection openings in the insert cavities of the present invention. 
           [0032]      FIG. 18  shows a top view of the stator vane with the two sequential cooling inserts and the flow direction from the two cooling air supply and discharge openings of the present invention. 
           [0033]      FIG. 19  shows a cross section side view of the turbine stator vane with the two sequential cooling inserts and flow paths of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    To solve problems of the current state-of-the-art and other methods utilizing pressures higher than compressor exit (over-pressurized cooling supply air) recirculated, the present invention proposes the use of multiple feed and extraction tubes consisting of supplies from over-pressurized air and compressor bled flows, organized at the vane Outer Diameter (OD). The present invention is shown in conceptual form in the  FIGS. 1-4 , but not limited to the shown orientation. 
         [0035]      FIG. 1  shows a stator vane  10  with a first cooling circuit  11  for a forward section of the airfoil and a second cooling circuit  12  for an aft section of the airfoil. Both cooling circuits  11  and  12  are higher pressure cooling air that first provides cooling for the stator vane  10  and second has enough remaining pressure to be discharged into the combustor along with the compressed air discharged from the compressor.  FIG. 1  shows two high pressure cooling circuits, but could have only one high pressure cooling circuit where the spent cooling air is discharged into the combustor. 
         [0036]      FIG. 2  shows a side view of a stator vane with cooling circuits according to the present invention where a higher pressure cooling air is used along with a lower pressure cooling air to provide cooling for the airfoil as well as the endwalls and the hooks of the stator vane. A higher pressure cooling air flows into the higher pressure cooling air feed tube  13 , which then flows thru an internal airfoil cooling circuit  14  to provide cooling for the airfoil of the stator vane  10 . The higher pressure spent cooling air then flows out from the airfoil through exit tube  15  where the spent cooling air is discharged into the combustor. This higher pressure cooling air can be merged with compressor outlet air in a diffuser positioned between the compressor outlet and the combustor inlet. The higher pressure cooling air circuit is a closed loop cooling circuit in which none of the cooling air is discharged out film holes into the hot gas stream passing thru the turbine. In another embodiment of the present invention, some of the stator vane cooling air can be used to provide cooling to the trailing edge and even the leading edge of the airfoil that is discharged into the hot gas stream in order to adequately cool these sections of the airfoil. 
         [0037]    The OD endwall and ID endwall and hooks of the stator vane  10  is cooled using lower pressure cooling air such as that bleed off from the compressor. A lower pressure cooling air feed tube  16  delivers lower pressure cooling air to the vane  10  to provide cooling for the OD endwall cavity  17  and the ID endwall cavity  18  and surrounding areas thru a lower pressure cooling air passage  19  within the airfoil of the vane  10 . The lower pressure cooling air can be discharged into the hot gas stream thru exit  21  and other exits including trailing edge exit holes or other exit holes in the airfoil. By using lower pressure cooling air instead of the high pressure cooling air in places that discharge the spent cooling air from the vane and into the hot gas stream, higher pressure seals are not required. If the higher pressure cooling air was used in the places where the lower pressure cooling air is used, the higher pressure cooling air would produce a large cooling air leakage thru the seals and into the hot gas stream. Thus, less higher pressure cooling air would be available for discharge into the combustor after cooling of the stator vane and surrounding areas. 
         [0038]      FIG. 3  shows a doublet stator vane segment in which the vane segment has two airfoils extending between the endwall cavities.  FIG. 3  shows a turbine vane carrier  22  with an OD platform  23 , a lower pressure feed tube  16  and a higher pressure feed tube  13 . The higher pressure exit tube  15  and the lower pressure cooling passage  19  formed within the airfoil is shown in  FIG. 3  for the two airfoils. A second lower pressure feed tube  16  is shown in the OD endwall.  FIG. 4  shows a similar arrangement for a single airfoil stator vane segment. 
         [0039]    The higher pressure cooling air circuit and the lower pressure cooling air circuit are separate cooling circuits and not in fluid communication to reduce any leakages. The feed and exit tubes  13  and  15  in  FIG. 2  prevent the higher pressure cooling air from leaking into the lower pressure cooling air of the OD endwall cavity  17 . The lower pressure cooling air feed tube  16  is formed as a hole in the turbine vane carrier to the OD cavity. The lower pressure feed tube  16  can also be sourced to adjacent ring segments through mounting hooks on the vane. 
         [0040]    The lower pressure cooling air source also feeds the ID cavity  18  cooling through a bypass cooling channel  19  within the vane. A second form fitted tube is connected directly to the vane OD cooling exit passage  17 , following a closed loop design for the over-pressurized air. Utilizing this closed loop design in conjunction with the multi-feed multi-pressure supply allows higher thermal efficiency, higher power output, but minimal leakage of over-pressurized cooling air into the gas-path. 
         [0041]      FIG. 5  shows one embodiment of a combined cycle power plant of the present invention which makes use of the turbine stator vane cooling circuit of  FIGS. 1-4 . The power plant includes a high spool with a high pressure compressor (HPC)  51  driven by a high pressure turbine (HPT)  52  from a hot gas stream produced in a combustor  53  where the high spool drives an electric generator  55 . A low spool or turbocharger includes a low pressure compressor (LPC)  62  driven by a low pressure turbine (LPT)  61  that is driven by turbine exhaust from the HPT  52 . The LPC includes a variable inlet guide vane assembly to regulate the speed of the low spool. The LPC  62  delivers compressed air to the HPC  51 . An intercooler  65  in compressed air line  67  cools the compressed air from the LPC  62 . Regulator valve  66  is in the compressed air line  67 . A boost compressor  56  with valve  57  can be used to deliver low pressure air to the inlet of the HPC  51  in certain situations. 
         [0042]      FIG. 6  shows another version of the combined cycle power plant of the present invention in which the turbine stator vanes are cooled using compressed air from the compressed air line  67 . Some of the compressed air from the line  67  is diverted into a second intercooler  71  and then further compressed by a boost compressor  72  driven by a motor  73  to a higher pressure than the outlet pressure of the HPC  51  so that the turbine stator vanes  76  can be cooled and the spent cooling air can be discharged into the combustor  53  through spent cooling air line  77 . The higher pressure cooling air feed tube  13  and exit tube  15  of the vane in  FIG. 2  would be lines  75  and  77  in  FIG. 6 . The lower pressure cooling air delivered to the lower pressure cooling air feed tube  16  would be discharged from the endwall cavities and into the hot gas stream passing through the turbine  52 . 
         [0043]      FIG. 7  shows another embodiment of the combined cycle power plant similar to the  FIG. 6  embodiment in which only one intercooler  65  is used to cool both the compressed air going to the HPC  51  and to the boost compressor  72 . 
         [0044]      FIGS. 8 through 19  show various features of the turbine stator vane with the closed loop cooling circuit for use in the industrial gas turbine engine of the present invention in which the cooling air used for the stator vane is discharged into the combustor instead of into the hot gas stream in the turbine.  FIG. 2  shows the turbine stator vane with inlet and outlet tubes  13  and  15  for the supply and return of the cooling air in the vane.  FIGS. 8 through 19  show various details of the stator vane cooling circuit that includes two sequential impingement cooling inserts. 
         [0045]    In  FIG. 8 , the stator vane  80  includes an airfoil  81  extending between an inner endwall and an outer endwall, and a cooling air inlet  82  and a cooling air outlet  83 . Two sequential impingement cooling inserts are shown in the cavities of the vane airfoil  81 . 
         [0046]      FIG. 9  shows the vane airfoil without the two inserts. The airfoil includes a number of internal cooling air passages  84  in which the two inserts are located.  FIG. 10  shows the two sequential impingement cooling inserts  90  as an assembly outside of the airfoil. 
         [0047]      FIG. 11  shows a detailed view of the leading edge (forward) cooling insert  95  with a leading edge coolant turn passage  93 , multiple rows of impingement cooling holes  91  extending in a chordwise direction of the airfoil, and cooling air return openings  92  extending in a spanwise direction of the airfoil.  FIG. 12  shows a detailed view of a section of the trailing edge (aft) cooling insert  96  with a trailing edge turn passage  94  as well as multiple rows of impingement cooling holes  91  and cooling air return openings  92 . Each of the two impingement cooling inserts  95  and  96  is formed with alternating outer surfaces in which the impingement holes  91  are located and inner surfaces that form spent impingement cooling air return channels in which the spent impingement cooling air is collected. Inside these inner surfaces are located cooling air return openings  92  in which the spent impingement cooling air flows through and into spanwise extending channels to channel the cooling air to the next location. 
         [0048]      FIG. 13  shows the two (forward and aft) impingement cooling inserts  95  and  96  from the front of the pressure wall side with the leading edge coolant return passage  93  and the trailing edge coolant return passage  94 .  FIG. 14  shows the forward and aft insert assembly  90  from the rear of the pressure wall side. The arrow on the top side pointed down shows the coolant supply direction. The coolant flows into the channel in a middle section of the airfoil and flows downward and out the impingement holes, then is collected in the return channels and flows through the return openings and into the channel that flows upward. The two curved arrows at the bottom of  FIGS. 13 and 14  represent this coolant turn. As the coolant flows upward, the cooling air flows out through the impingement holes  91  and then into the return channels and through the return openings  92  and into the channel that flows upward. The cooling air then flows through the two turn passages  93  and  94 , and then flows down again in the last channels and through impingement holes  91  along the leading edge and trailing edge of the airfoil. The suction side of the inserts also includes these rows of impingement cooling holes  91  and the return openings  92  to provide impingement cooling to the suction side wall of the airfoil as well. 
         [0049]      FIG. 15  shows a top side of the vane with the cooling air inlet  82  and a cooling air outlet  83  and an outer diameter (OD) cover plate  85  that encloses the upper section of the vane cooling circuit with the two turn channels  93  and  94 .  FIG. 16  shows a bottom side of the vane with inner diameter (ID) cover plate  86  that encloses the bottom section of the vane cooling circuit and forms the turn channels for the cooling air in the two inserts.  FIG. 19  shows a side view of the vane with the two inserts and the OD and ID cover plates  85  and  86  with the cooling flow directions. 
         [0050]      FIG. 17  shows the vane without the two inserts. The cooling air inlet  82  and a cooling air outlet  83  is shown, and the number of internal cooling air passages  84  in which the two inserts would fit. A number of cooling air feed passages  87  are shown in which cooling air is delivered to the two inserts or from the two inserts.  FIG. 18  shows a top view of the vane and the two inserts and the flow directions of the cooling air to and from the inserts. Cooling air flows into the inlet  82  and then along a channel in the outer diameter endwall and into the feed passages  87  that open into the forward and aft inserts  95  and  96 . The cooling air then flows through each insert through the rows of impingement holes  91  and return openings  92  to cool each wall of the airfoil, and then flows out from each insert and along channels in the outer endwall and into the outlet  83 . From the cooling air inlet  82  to the cooling air outlet  83 , the cooling air passes through the inserts and the airfoil in a closed loop cooling circuit in which none of the cooling air is discharged out from the airfoil and into the hot gas stream passing around the vane. 
         [0051]      FIG. 19  shows a side view of the two inserts  95  and  96  within the vane airfoil  81  with the outer and inner cover plates  85  and  86  and the cooling air feed passages  87 .