Patent Application
20070231138
(1) Field of the Invention
The present invention relates to enhanced convective cooling resulting from adding a U-shaped divider rib dividing a plurality of cooling fluid channels in a serpentine cooling passage.
(2) Prior Art
Vanes currently used in gas turbine engines use a three pass serpentine cooling passageway 10 such as that shown in
There is a need for a cooling passageway for the airfoil portion that has an improved flow structure and better heat transfer properties.
In accordance with the present invention, a cooling passageway is provided which has an improved flow structure and improved heat transfer properties.
In accordance with the present invention, a cooling passageway for use in an airfoil portion of a turbine engine component having a pressure side wall and a suction side wall is provided. The cooling passageway broadly comprises a serpentine flow passageway through which a cooling fluid flows, which passageway has an inlet through which cooling fluid is introduced into the passageway, an inlet channel, an intermediate channel, and an outlet channel, and a divider rib extending from a location in the inlet channel to a termination in the intermediate channel.
Further in accordance with the present invention, a turbine engine component is provided. The turbine engine component broadly comprises an airfoil portion having a suction side wall and a pressure side wall, and a serpentine cooling passageway within the airfoil portion located between the suction side wall and the pressure side wall. The serpentine cooling passageway has an inlet channel, an intermediate channel, a first turn fluidly connecting the inlet channel to the intermediate channel, an outlet channel, and a second turn fluidly connecting the intermediate channel to the outlet channel. The inlet channel communicates with a source of cooling fluid via a fluid inlet. The cooling passageway further has means for dividing the flow within the inlet channel and a portion of the intermediate channel into two flow streams for providing improved heat transfer coefficients.
Other details of the enhanced serpentine cooling with U-shaped divider rib 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.
Referring now to
The U-shaped divider rib 124 allows a split of the cooling fluid entering the passageway 110 into two flow streams to be more easily controlled and to be more uniformly distributed. The U-shaped or arcuately shaped portion 126 of the divider rib 124 assists in guiding the cooling fluid around the first turn 116 in each of the channels 114A and 114B.
As can be seen in
The presence of the U-shaped divider rib 124 in the intermediate channel 118 provides each of the channels 118A and 118B with an improved aspect ratio. As used herein, the term “aspect ratio” means the length of the channel divided by the height. It has been found that as a result of the presence of the U-shaped divider rib 124 in the intermediate channel 118, the aforementioned double vortex flow structure induced by the trip strips 130 begins to develop sooner and generates higher heat transfer coefficients earlier in the passageway 110.
As can be seen in
After the two flows are joined in the undivided portion of the channel 118, the joined flow passes around the second turn 120 and into the outlet channel 122. If desired, the outlet channel 122 may also be provided with a plurality of spaced apart, angled trip strips 130. Preferably, the trip strips 130 are staggered one half pitch apart from suction side wall 132 to pressure side wall 134. The cooling flow may exit the outlet channel 122 in any suitable manner known in the art such as through a series of film cooling holes (not shown) or through a plurality of cooling passageways (not shown) in the trailing edge portion 113 of the airfoil 111.
In an alternative embodiment of the present invention, the U-shaped divider rib 124 may be started at a location several hydraulic diameters downstream of the inlet 112 such as 0.5 to 5 hydraulic diameters. As used herein, the term “hydraulic diameter” is approximately 4 times the area of the inlet channel divided by the wetted perimeter of the inlet channel. Placing the beginning of the U-shaped diameter rib 124 in such a location reduces the head loss associated with the split of the incoming cooling fluid flow.
Referring now to
Turbine engine components, such as blades and vanes, which utilize the enhanced serpentine cooling passageway of the present invention may have both a low cooling air supply pressure and a small cooling flow allocation. The addition of the U-shaped divider rib 124 has several heat transfer benefits and will ensure the success of this configuration without changing the cooling air supply pressure or flow rate. In the present invention, the cavity area is reduced by the size of the divider rib 124, improving the amount of cooling flow per unit area. The aspect ratio of the trip strip channels in the intermediate channels 114 and 118 is dramatically improved, allowing a desirable double vortex structure intended by the angled trip strips 130 to develop quickly. Additionally, the flow around the first turn 116 is completely guided, controlling the loss around the first turn 116, forcing the flow to distribute more evenly around the turn 116, and eliminating flow separation downstream of the turn 116.
A serpentine cooling passageway with a U-shaped divider rib in accordance with the present invention will be superior to a five pass serpentine solution in convective applications where the available cooling supply flow rate and pressure are limited due to the lower level of additional pressure loss. It also allows targeting of internal heat transfer coefficients to a second passage of the inner or outer loop, where a five pass serpentine in satisfying the continual convergence criteria is more limited. The U-shaped rib of the present invention is also preferred to simple divided passages due to both the improved flow structure around the turn and the elimination of the loss associated with dividing a channel in a region with non-negligible Mach number flow, and/or where the flow is not well developed. To achieve full benefit, care must be taken to configure the inner and outer turns properly. The U-shaped divider rib 124 allows tailoring of internal heat transfer coefficients to the inner or outer channel, offering improved design flexibility.
The improvements provided by the cooling passageway of the present invention will lead to greatly increased airfoil oxidation and thermal mechanical fatigue (TMF) cracking life in the mid-body of the airfoil portion of the turbine engine component.
It is apparent that there has been provided in accordance with the present invention an enhanced serpentine cooling with a U-shaped divider rib 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 any unforeseeable alternatives, modifications, and variations that fall within the broad scope of the appended claims.
