Apparatus for acoustic damping and operational control of damping, cooling, and emissions in a gas turbine engine

Abstract

Acoustic damping resonators ( 60, 62, 76, 78 ) formed in pockets ( 32 ) between reinforcing ribs ( 30 ) in a grid of ribs on the outer surface of a wall ( 74 ) surrounding a combustion gas flow path ( 18 ). Each resonator has a perforated cover plate ( 64 A-C) spanning between sides formed by the ribs ( 30 ). Film cooling exit holes ( 44 ) are provided in the wall ( 74 ) under each resonator. Resonating chambers ( 48 A-C) of different volumes may be provided on the wall to damp different unwanted frequencies. Different sets of resonators with different volumes may be separately controlled by respective airflow control manifolds ( 66 ) via throttle valves ( 68, T 1 -T 3 ). Control logic ( 70 ) may control the valves based on frequency/airflow response functions ( 80, 82 ) for each size of resonator to optimize damping and cooling and to lower emissions over varying engine operating conditions.

The invention claimed is: 
     
         1 . Apparatus for acoustic damping in a gas turbine engine, comprising:
 a combustion gas flow directing structure comprising a wall that lines a flow path for a combustion gas, the wall being surrounded by compressed air at higher pressure than a pressure of the combustion gas;   a plurality of pockets formed by a grid of ribs on an outer surface of the wall;   a perforated resonator plate covering one of the pockets forming a first resonator comprising a first resonating chamber having a first volume in the pocket;   a plurality of air exit holes in the wall under the resonating chamber, the holes acting as Helmholtz resonator ports for the first resonating chamber and as film cooling holes for cooling an inner hot surface of the wall; and   a first airflow manifold covering the first resonator and metering a first inflow of the compressed air to the first resonator.   
     
     
         2 . The apparatus of  claim 1 , wherein the first inflow metering is controlled by a first throttle valve connected to a control logic that varies a position of the first throttle valve based on varying operating conditions of the engine. 
     
     
         3 . The apparatus of  claim 2 , wherein the control logic controls the first throttle valve to meter the first inflow in inverse proportion to engine load, wherein the first throttle valve reduces the first inflow as an engine load increases, and increases the first inflow as the engine load decreases. 
     
     
         4 . The apparatus of  claim 1 , wherein the flow directing structure comprises a flow accelerating geometry that accelerates the combustion gas in the flow path and reduces static pressure of the combustion gas in the flow path by constricting a sectional flow area of the combustion gas flow path. 
     
     
         5 . The apparatus of  claim 4 , wherein the flow directing structure comprises a transition duct comprising an upstream conic portion and a downstream exit piece. 
     
     
         6 . The apparatus of  claim 1 , wherein the ribs are reinforcing ribs that are cast into the flow directing structure, wherein each rib comprises a rib height above the outer surface of the wall, wherein the resonator plate is attached to the reinforcing ribs at a first height that separates the resonator plate from the outer surface of the wall, and wherein the resonator plate is not attached directly to the outer surface of the wall. 
     
     
         7 . The apparatus of  claim 6 , further comprising a second resonator plate covering a second one of the pockets at a second height above the outer surface of the wall, forming a second resonator with a second resonating chamber with a different volume than the first volume. 
     
     
         8 . The apparatus of  claim 7 , wherein the first airflow manifold covers both the first and second resonators, and the first inflow metering is controlled by a first throttle valve connected to a control logic that varies a position of the first throttle valve based on an operating condition of the engine;
 wherein the control logic controls the first throttle valve to meter the first inflow in inverse proportion to engine load, wherein the first throttle valve reduces the first inflow as an engine load increases, and increases the first inflow as the engine load decreases.   
     
     
         9 . The apparatus of  claim 6 , further comprising:
 a second resonator formed by a second resonator plate covering a second one of the pockets, wherein the second resonator comprises a second resonating chamber having a different volume than the first volume; and   a second airflow manifold covering the second resonator and metering a second inflow of the compressed air to the second resonator at a different flow rate than a metered flow rate of the first inflow during at least some operating conditions of the engine.   
     
     
         10 . The apparatus of  claim 9 , wherein the first and second inflows are controlled by respective first and second throttle valves connected to a control logic that varies a position of the each throttle valve based on an operating condition of the engine. 
     
     
         11 . The apparatus of  claim 9  wherein the first and second resonating chambers have the same height above the outer surface of the wall. 
     
     
         12 . Apparatus for acoustic damping in a gas turbine engine, comprising:
 a wall surrounding a flow path for a combustion gas;   a plenum for compressed air around an outer surface of the wall;   a first and second plurality of acoustic damping resonators on the outer surface of the wall, the resonators of the first plurality each comprising a resonating chamber with a first volume, and the resonators of the second plurality each comprising a resonating chamber with a second volume that is different from the first volume;   film cooling exit holes in the wall under each chamber;   a first airflow control manifold that meters a first inflow of the compressed air to the first plurality of acoustic damping resonators; and   a second airflow control manifold that meters a second inflow of the compressed air to the second plurality of acoustic damping resonators;   wherein the first and second manifolds meter the first and second inflows by different amounts from each other during at least some operating conditions of the engine, and both manifolds reduce a pressure of the compressed air provided to the resonators compared to a pressure of the compressed air in the plenum.   
     
     
         13 . The apparatus of  claim 12 , wherein at least some of the first resonating chambers have the same height as at least some of the second resonating chambers. 
     
     
         14 . The apparatus of  claim 12 , wherein the first and second airflow control manifolds comprise respective first and second throttle valves that meter the respective first and second inflows, wherein the throttle valves are connected to a control logic that controls the throttle valves to vary each of the first and second inflows based on a set of damping frequency/airflow response curves of the resonators to optimize acoustic damping, cooling, and combustion temperature in the engine under varying operating conditions of the engine. 
     
     
         15 . The apparatus of  claim 12 , wherein the wall comprises a flow accelerating geometry that accelerates the combustion gas in the flow path to more than mach 0.3, and reduces the static pressure of the combustion gas in the flow path by constricting a sectional flow area of the combustion gas flow path; wherein the resonating chambers are formed in pockets between reinforcing ribs cast on the outer surface thereof. 
     
     
         16 . The apparatus of  claim 12 , further comprising a third plurality of acoustic damping resonators on the outer surface of the wall, each resonator of the third plurality comprising a resonating chamber of different volume than the chamber volumes of the first and second pluralities; wherein the first second and third pluralities of damping resonators in combination damp at least some frequencies over range of 300-4000 Hz. 
     
     
         17 . The apparatus of  claim 12 , wherein the first and second inflows are metered by respective valves controlled by control logic that controls acoustic damping of a range of acoustic frequencies both above and below 1000 Hz, and controls a combination of acoustic damping, cooling, and emission control in a combustion section of the gas turbine engine over a range of operating conditions. 
     
     
         18 . The apparatus of  claim 12 , wherein the respective inflows of the compressed air to the first and second pluralities of resonators are variably metered by respective first and second throttles to control CO and NOx emissions and to control damping of frequencies both above and below 1000 Hz over a range of engine operating conditions under control of a control logic based on a set of frequency/airflow response functions for each of the first and second pluralities of resonators.