BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing cooling effectiveness versus film effectiveness for a turbine engine component;
FIG. 2A shows an airfoil portion of a turbine engine component having a pressure side cooling microcircuit embedded in the pressure side wall and a suction side cooling microcircuit embedded in the suction side wall;
FIG. 2B is a schematic representation of a pressure side cooling microcircuit used in the airfoil portion of FIG. 2A;
FIG. 2C is a schematic representation of a suction side cooling microcircuit used in the airfoil portion of FIG. 2A;
FIG. 3 illustrates the cooling flow distribution for a turbine engine component with serpentine microcircuits embedded in the airfoil walls;
FIG. 4 is a graph illustrating the low back flow margin for the third leg of the pressure side circuit of FIG. 2B;
FIG. 5 is a schematic representation of a pressure side cooling scheme in accordance with the present invention; and
FIG. 6 is a schematic representation of an alternative pressure side cooling scheme in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring now to FIG. 5, there is shown a schematic representation of pressure side cooling scheme for a turbine engine component 100, such as a turbine blade, having an airfoil portion 102. As can be seen from this figure, the pressure side of the airfoil portion 102 is provided with two peripheral serpentine circuits 104 and 106 offset radially from each other to minimize the heat pick-up in each circuit. Film cooling is provided separately by shaped holes from the main core cavities. The circuits 104 and 106 are embedded within the pressure side wall.
The first circuit 104 has an inlet 108 for receiving a flow of cooling fluid from a source (not shown). The cooling fluid flows from the inlet 108 into a first leg 110 and then into a second leg 112. From the second leg, the cooling fluid flows into a third or outlet leg 114 through one or more tip holes 150. As can be seen from FIG. 5, the first two legs 110 and 112 of the cooling circuit are only present in a lower span of the airfoil portion 102, i.e, below the mid-span line 120 for the airfoil portion 102.
The circuit 106 is formed in the upper span of the airfoil portion 102, i.e. above the mid-span line 120. The circuit 106 has a first leg 122 which has an inlet which communicates with an internal supply cavity (not shown). Cooling fluid from the first leg 122 flows into a second leg 124 and then into the outlet leg 114. Thus, the upper part of the pressure side is convectively cooled.
The cooling scheme as shown in this embodiment, also includes a plurality of film cooling holes 115. The film cooling holes may be used to form a film of cooling fluid over external surfaces of the pressure side including a trailing edge portion. The film cooling holes 115 may be supplied with cooling fluid via one or more main core cavities such as one or more of cavities 41 shown in FIG. 3.
The cooling circuits 104 and 106 may be formed using any suitable technique known in the art. For example, the circuits may be formed using a combination of refractory metal core technology and silica core technology. For example, refractory metal cores may be used to from the lower span peripheral core 130 and the upper span peripheral core 132, while silica cores may be used to form the trailing edge structure 134 and the airfoil main body 136.
Referring now to FIG. 6, there is shown another cooling scheme for the pressure side of an airfoil portion of a turbine engine component. In this scheme, the pressure side is provided with a first cooling circuit 204 and a second cooling circuit 206. The first cooling circuit 204 is a serpentine cooling circuit having an inlet leg 208 which communicates with an inlet 210 which in turn communicates with a source of cooling fluid (not shown). The inlet leg 208 extends along the lower and upper span of the airfoil portion and communicates with a second leg 212 which in turn communicates with an third or outlet leg 214. The cooling fluid exits the outlet leg 214 through one or more tip holes 250. The cooling circuit 206 has an inlet leg 216 which communicates with a trailing edge inlet 218 which is separate from the inlet 210. The inlet leg 216 provides cooling fluid to a radially extending outlet leg 220 which extends over the lower and upper spans of the airfoil portion. A plurality of film slots 222 may be provided so that cooling fluid from the outlet leg 220 flows over the pressure side of the airfoil portion 102.
The cooling circuits 204 and 206 may be formed using any suitable technique known in the art. For example, the cooling circuits 204 and 206 may be formed using refractory metal cores for the lower span 230 and the upper span 232. Silica cores may be used to form the main body core 234 and the trailing edge silica core 236.
The suction side of the airfoil portion 102 may be provided with an embedded serpentine cooling circuit such as that shown in FIG. 2C.
In both pressure side cooling arrangements shown in FIGS. 5 and 6, the heat pick-up is minimized and, as a result, these peripheral cooling arrangements can be used for blades with higher aspect ratios and increased surface area. In these arrangements, the circuits are also shorter which reduces the pressure drop associated with each circuit. As the radial height of each circuit is minimized, the straight portions of the circuits are minimized, whereas the turning portions of the circuits are increased. This leads to higher internal heat transfer coefficients without the need for heat transfer augmentation.
It is apparent that there has been provided in accordance with the present invention multi-peripheral serpentine microcircuits for high aspect ratio blades which fully satisfy 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 detailed description. Accordingly, it is intended to embrace those alternatives, modifications, and variations as fall within the broad scope of the appended claims.
Patent Application
20080056909
