Patent Application
20100247328
(1) Field of the Invention
The present invention relates to a turbine engine component, such as a turbine blade, having a cooling microcircuit which is easy to fabricate and which has a plurality of cooling devices for effecting heat pick-up.
(2) Prior Art
For an existing cooling microcircuit blade design configuration, such as that illustrated in the two-dimensional span of
Thus, there is a need for an improved cooling microcircuit which can be used in turbine engine components such as turbine blades.
In accordance with the present invention, there is provided a turbine engine component, such as a turbine blade, having a cooling microcircuit whose assembly is not complex.
Further, in accordance with the present invention, there is provided a turbine engine component which broadly comprises at least one cooling circuit having a plurality of legs through which a cooling fluid flows, and a plurality of cooling devices in at least one of the legs. Each of the cooling devices has a heat transfer multiplier in the range of from 1.8 to 2.4 and a reattachment length in the range of from 1.9 to 2.5.
Also, there is provided in accordance with the present invention, a cooling microcircuit for use in a turbine engine component which broadly comprises a first leg for receiving a cooling fluid, a second leg for receiving the cooling fluid from the first leg, and a third leg for receiving the cooling fluid from the second leg. At least one of the first and second legs contains a plurality of cooling devices. Each of the cooling devices has a heat transfer multiplier in the range of from'1.8 to 2.4 and a reattachment length in the range of from 1.9 to 2.5.
Other details of the microcircuit cooling for blades of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.
One way to compensate for the assembly difficulties in the prior art is to combine different cores together. In this context, it is also desirable to increase the size of the combined microcircuits without losing thermal characteristics. In general, cooling microcircuits have banks of pedestals as cooling devices to enhance heat pick-up. While employing these cooling devices in the cooling microcircuits, it is also desirable to minimize their number for the same heat pick-up capability.
In general, at the pedestal to wall junction, there are flow horseshoe vortices due to protrusion-endwall interaction, which contribute to the heat transfer. Also, as the flow passes these pedestals, flow circuits reattach downstream from a shear layer separation. These effects are common to pedestals of different cross-sectional areas, namely cylinder, cube, and diamond-shaped pedestals. As the cross sectional shape of the pedestal changes, the flow can become more complex. For instance, the flow in the cube vicinity is highly three dimensional and dominated by a number of vortices far more complex than those around a cylinder.
From
For a diamond type pedestal, the value of the heat transfer multiplier recovers downstream to reach a maximum of about 2.4 heat transfer enhancement (reference being the flat plate heat transfer) at an x/d of 2.5. Not only is this the farthest location of reattachment induced enhancement downstream to the obstacle, but also it has the highest value of maximum heat transfer multiplier. The key factor responsible for this effect is the special flow characteristics related to diamond shaped pedestals. It is dominated by highly turbulent delta-wing vortices as opposed to the commonly observed, recirculating bubble. These vortices substantially elevate the surface heat transfer underneath their tracks. It is expected that such influence persists further downstream as the shear layer reattached to the endwall.
In accordance with the present invention, it is desirable to use a cooling device having a reattachment length in the range of 1.9 to 2.5 and a heat transfer multiplier relative to flat plate heat transfer in the range of from 1.8 to 2.2, preferably from 2.2 to 2.4.
The diamond shaped pedestal has the strongest reattachment-induced enhancement with the widest spread in the wake region. In addition, its reattachment length is also the longest.
Referring now to
As can be seen from
As noted above, each cooling device 80 could have a cube shape. When using a cube shaped cooling device, one of the sides of the cube should be oriented substantially normal to the direction of flow of the cooling fluid in the leg in which the cooling device 80 is located.
As can be seen from
The cooling microcircuit 20 may be provided with a third leg 36 in which the coolant flows radially upward. The tip circuit 32 also may comprise a plurality of spaced apart flow passages 72. Each flow passage 72 may have an inlet which communicates with the third leg 36 of the cooling microcircuit 20 so as to receive coolant therefrom. Each cooling circuit passage 70 and 72 has a fluid outlet or exit 33 which allows cooling fluid to flow over a surface of the airfoil portion 12. Preferably, the exits 33 are configured to allow the coolant to exit on the pressure side 35 of the airfoil portion 12. The tip cooling exits 33 from the circuits 30 and 32 may extend from a point near the leading edge 44 to a point near the trailing edge 50 of the airfoil portion 12. By providing the cooling microcircuit arrangement described herein, three separate circuits make up one unit and thus facilitate the assembly process.
A root inlet refresher leg 38 may be fabricated within the root portion 16. The root inlet refresher leg 38 is in fluid communication with the third leg 36 and may be used to insure adequate cooling flow in the third leg 36. The root inlet refresher leg 38 may communicate with any suitable source (not shown) of cooling fluid such as engine bleed air.
As can be seen from the foregoing description, an integral main body and tip microcircuit arrangement 20 has been provided. The turbine engine component 10 is cooled convectively in this way.
If desired, exit tabs 40 forming film slots 42 may be provided in the legs 26 and/or 28. The exit tabs 40 and film slots 42 allow coolant fluid to flow from the legs 26 and/or 28 onto a surface of the airfoil portion. The surface may be the pressure side surface 35 or the suction side surface 37. Fluid exiting the slots 42 helps form a cooling film over one or more of the exterior surfaces of the turbine engine component 10. Such film slots 42 may be useful in an open-cooling system.
If desired, the leading edge 44 of the airfoil portion 12 may be provided with a plurality of fluid outlets or exits 46 which allow a film of coolant to flow over the leading edge portions of the pressure side 35 and the suction side 37 of the airfoil portion 12. The outlets or exits 46 may be supplied with coolant from a supply cavity 48. The supply cavity 48 may communicate directly with a source (not shown) of cooling fluid, such as engine bleed air, or alternatively, the supply cavity 48 may be in fluid communication with the first leg 26.
The cooling microcircuit of the present invention may also be used in a closed loop system without film cooling for industrial gas turbine applications where the external thermal load is not as high as that for aircraft engine applications.
The cooling microcircuit arrangement of the present invention may be formed using any suitable technique known in the art. In a preferred method of forming the cooling microcircuit, one or more sheets formed from a refractory metal material may be configured in the shape of the cooling microcircuit arrangement 20 including the inlet 24 and the root inlet refresher leg 38, the legs 26, 28, and 36, the tip cooling microcircuits 30 and 32, the exits 33, the tabs 40, and the film slots 42. The refractory metal material sheets may be placed or positioned within a mold cavity. Thereafter, the turbine engine component 10 including the airfoil portion 12, the platform 14, and the root portion 16 may be cast from any suitable metal known in the art such as a nickel based superalloy, a titanium based superalloy, or an iron based superalloy. After the turbine engine component has been cast, the refractory metal material sheets may be removed using any suitable means known in the art, leaving the cooling microcircuit arrangement 20 of the present invention.
It is apparent that there has been provided in accordance with the present invention microcircuit cooling for blades which fully satisfies the objects, means, and advantages set forth hereinbefore. While the present invention has been described in the context of specific embodiments thereof, other unforeseeable alternatives, modifications, and variations may become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.
