Combustor chamber cooling

Abstract

A gas turbine engine combustor which is cooled by a hybrid cooling apparatus and method. Heat shields cooled by impingement cooling air are present at an upstream section of the combustor liners and exhausted impingement cooling air is substantially discharged outside of the primary zone of the combustor chamber. The single-skinned downstream section of the combustor liners is cooled by effusion cooling.

1 . A combustor for a gas turbine engine comprising: inner and outer liners spaced apart from each other to define a chamber therebetween including a primary zone adjacent an upstream end of the chamber and a secondary zone downstream of the primary zone, the upstream end being closed by a dome, a dome heat shield disposed within the chamber, adjacent and spaced apart from the dome, an inner liner heat shield disposed within the chamber, adjacent and spaced apart from the inner liner, an outer liner heat shield disposed within the chamber, adjacent and spaced apart from the outer liner, the inner and outer liner heat shields extending from the upstream end of the chamber over the primary zone and terminating at the secondary zone, the inner and outer liners and the inner and outer liner heat shields defining a plurality of apertures therein for introducing dilution air jets into the chamber, the combustor including a plurality of impingement holes defined in the dome and inner and outer liners for directing impingement cooling air therethrough and into the combustor to impinge on a cold side of the respective heat shields, and a discharging apparatus to direct exhausted impingement cooling air discharged from the cold side of the respective heat shields to flow along and substantially parallel to a hot side of the respective inner and outer liner heat shields, the combustor further including a plurality of effusion holes defined in a section of the inner and outer liners free of coverage by the respective inner and outer liner heat shields, the effusion holes directing effusion cooling air therethrough and into the combustor to effusion cool said section of the inner and outer liners. 
     
     
         2 . The combustor as defined in  claim 1  wherein the effusion holes defined in said section of the inner and outer liners are located downstream of the apertures for the dilution air jets. 
     
     
         3 . The combustor as defined in  claim 1  wherein the dome heat shield is disposed with respect to the inner and outer liner heat shields to define a respective gap between the inner liner heat shield and the dome heat shield, and between the outer liner heat shield and the dome heat shield to discharge a portion of the exhausted impingement cooling air in a cooling air film along the hot side of the respective inner and outer liner heat shield. 
     
     
         4 . The combustor as defined in  claim 1  wherein a swirler attached to the dome comprises cooling passages for introducing cooling air into the combustor and a cooling air director to generate a cooling air film along and substantially parallel to the hot side of the dome heat shield. 
     
     
         5 . The combustor as defined in  claim 4  wherein the cooling air introduced through the cooling passages in the swirler is independent from an air flow introduced by the swirler for combustion. 
     
     
         6 . The combustor as defined in  claim 1  wherein the discharging apparatus comprises a plurality of splash louvers on the cold side at a downstream end of the respective inner and outer liner heat shields to act as a film starter for a portion of the exhausted impingement cooling air discharged from the downstream end of the inner and outer liner heat shields. 
     
     
         7 . The combustor as defined in  claim 1  wherein the inner and outer liner heat shields comprise a plurality of effusion holes at a downstream end thereof for discharging a portion of the exhausted impingement cooling air into the secondary zone of the chamber. 
     
     
         8 . The combustor as defined in  claim 7  wherein the effusion holes defined in the inner and outer liner heat shields are located downstream of the apertures for the dilution air jets. 
     
     
         9 . The combustor as defined in  claim 1  wherein the dome heat shield and the inner and outer liner heat shields comprise a plurality of pin fins projecting from the cold side of the respective dome heat shield and the inner and outer liner heat shields, for convection cooling the respective heat shields. 
     
     
         10 . A method for hybrid cooling a combustor of a gas turbine engine comprising steps of:
 a) providing heat shield panels in a chamber of the combustor to protect respective upstream sections of inner and outer liners of the combustor, the upstream sections of the inner and outer liners substantially covering a primary zone of the chamber;   b) directing impingement cooling air for impingement cooling a cold side of the heat shield panels and then discharging a first portion of the impingement cooling air along and substantially parallel to a hot side of the heat shield panels and a second portion of the impingement cooling air into areas downstream of the heat shield panels, to thereby have the discharged cooling air substantially outside of the primary zone in order to reduce emission formation; and   c) directing cooling air into a downstream area of the chamber for effusion cooling of respective downstream sections of the inner and outer liners free of coverage by the heat shield panels.   
     
     
         11 . The method defined in  claim 10  further comprising a step of substantially restraining effusion cooling air within the chamber to an area downstream of dilution air jets, the dilution air jets being introduced into the chamber between the primary zone and a secondary zone. 
     
     
         12 . The method defined in  claim 10  wherein the heat shield panels in step (a) covers a dome of the combustor. 
     
     
         13 . The method defined in  claim 12  comprising a step of using a swirler attached to the dome to introduce cooling air independent from an air flow introduced by the swirler for combustion, to generate a cooling film along a hot side of a number of the heat shield panels covering the dome. 
     
     
         14 . The method defined in  claim 12  wherein step b) includes using gaps defined between a number of the heat shield panels covering the dome and a number of the heat shields covering the inner or outer liners to discharge the first portion of the impingement cooling air.