The application relates generally to gas turbine engines and, more particularly, to airfoil cooling.
Gas turbine engine design mainly focuses on efficiency, performance and reliability. Efficiency and performance both favour high combustion temperatures, which increase thermodynamic efficiency, specific thrust and maximum power output. Unfortunately, higher gas flow temperatures also increase thermal and mechanical loads, particularly on the turbine airfoils. This reduces service life and reliability, and increases operational costs associated with maintenance and repairs.
Therefore, there continues to be a need for new cooling schemes for turbine airfoils.
In one aspect, there is provided an internally cooled airfoil for a gas turbine engine, comprising a hollow airfoil body having opposed pressure and suction sidewalls defining therebetween a cooling passage, and a plurality of pedestals extending across said cooling passage from said pressure sidewall to said suction sidewall, wherein at least some of said pedestals have a trip-strip portion projecting laterally therefrom a distance less than the distance between two adjacent pedestals.
In a second aspect, there is provided an internally cooled airfoil for a gas turbine engine, comprising a hollow airfoil body having opposed pressure and suction sidewalls defining therebetween a cooling passage, a plurality of pedestals staggered in a trailing edge region of the cooling passage and extending from said pressure sidewall to said suction sidewall, and a plurality of trip-strips provided on an inner surface of at least one of said pressure and suctions sidewalls, each of said trip-strips having a proximal end attached to an associated one of said pedestals and a distal end spaced-apart from adjacent pedestals.
In accordance with a third aspect, there is provided a gas turbine engine component comprising a surface to be cooled by a flow of coolant, a plurality of pedestals staggered on said surface, and a plurality of trip-strips provided on said surface, each of said trip-strips having a proximal end attached to an associated one of said pedestals and a distal end spaced-apart from adjacent pedestals.
Reference is now made to the accompanying figures, in which:
The turbine section 18 may have various numbers of stages. Each stage comprises a row of circumferentially distributed stator vanes followed by a row of circumferentially distributed rotor blades.
Referring concurrently to
As mentioned above, the trip-strips 38 do not extend all the way from pedestal-to-pedestal. Rather, each trip-strip 38 has a free distal end 38a which is spaced from the adjacent pedestals (i.e. the trip-strips 38 do not interconnect the pedestals 36; the pedestals 36 are only interconnected by the pressure and suction sidewalls 24, 26).
As can be appreciated from
By providing trip-strips having a small height compared to the pedestal height, and by providing trip-strips that do not extend all the way from pedestal to pedestal, the coolant pressure drop may be minimized while still providing for enhanced heat transfer.
The trip-strips 38 may be oriented generally perpendicularly to the primary flow direction of the coolant flowing through the trailing edge region of the cooling passage 33. With this trip-strip orientation, the coolant flow path is still primarily back and forth. This contributes to avoiding creating vortex-like flow paths which would result in greater coolant pressure losses.
As shown in
The pedestals 36 and the trip-strips 38 may be integrally cast with the hollow airfoil body 22. The integration of the trip-strips 38 to the ends of the pedestals 36 has the advantage of being easier to cast than pedestals plus pin-fins.
The flow path through staggered pedestals in the trailing edge region of an internal cooling passage of an airfoil is back and forth as shown in
The increase in pressure loss as compared to pedestals alone is slight if the trip-strip height is small compared to the pedestal height, and if the trip-strip does not extend all the way from pedestal to pedestal.
As can be appreciated from the foregoing, the combination of pedestals and trip-strips contributes to enhanced heat transfer while minimizing the coolant pressure drop across these heat exchange promoting features. By so improving the airfoil cooling efficiency, the thermal stress on the airfoil can be reduced and, thus, the service life of the airfoil can be extended. Also, by integrating the trip-strips to the pedestals, the airfoil may be more easily cast than with conventional pedestals alone since a reduced number of integrated “Ped-Trip” features can be used for the same heat transfer.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, while the invention has been described in the context of a turbine vane, it is understood that the same principles could be applied to other types of internally cooled airfoils, including turbine blades. The same principles could also be applied to gas turbine engine components, such as shroud segments and combustor heat shields, as well as applications other than in gas turbine engines where a fluid flows through a passage to provide heat transfer to or from the walls of this passage. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.