Apparatus and methods for cooling platform regions of turbine rotor blades

A configuration of cooling channels through the interior of a turbine rotor blade, the turbine rotor blade including a platform at an interface between an airfoil and a root. In one embodiment, the configuration of cooling channels includes: an interior cooling passage that is configured to extend from a connection with a coolant source in the root to the interior of the airfoil; a platform cooling channel that traverses at least a portion of the platform; a turndown extension that includes a first section, which comprises a connection with the platform cooling channel, and a second section, which comprises a radially oriented cooling channel; and a connector that extends from a connector opening formed through an outer face of the root to a connection with the interior cooling passage and, therebetween, bisects the second section of the turndown extension.

BACKGROUND OF THE INVENTION

The present application relates generally to combustion turbine engines, which, as used herein and unless specifically stated otherwise, includes all types of combustion turbine engines, such as those used in power generation and aircraft engines. More specifically, but not by way of limitation, the present application relates to apparatus, systems and/or methods for cooling the platform region of turbine rotor blades.

A gas turbine engine typically includes a compressor, a combustor, and a turbine. The compressor and turbine generally include rows of airfoils or blades that are axially stacked in stages. Each stage typically includes a row of circumferentially spaced stator blades, which are fixed, and a set of circumferentially spaced rotor blades, which rotate about a central axis or shaft. In operation, the rotor blades in the compressor are rotated about the shaft to compress a flow of air. The compressed air is then used within the combustor to combust a supply of fuel. The resulting flow of hot gases from the combustion process is expanded through the turbine, which causes the rotor blades to rotate the shaft to which they are attached. In this manner, energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which then, for example, may be used to rotate the coils of a generator to generate electricity.

Referring toFIGS. 1 and 2, turbine rotor blades100generally include an airfoil portion or airfoil102and a root portion or root104. The airfoil102may be described as having a convex suction face105and a concave pressure face106. The airfoil102further may be described as having a leading edge107, which is the forward edge, and a trailing edge108, which is the aft edge. The root104may be described as having structure (which, as shown, typically includes a dovetail109) for affixing the blade100to the rotor shaft, a platform110from which the airfoil102extends, and a shank112, which includes the structure between the dovetail109and the platform110.

As illustrated, the platform110may be substantially planar. (Note that “planar,” as used herein, means approximately or substantially in the shape of a plane. For example, one of ordinary skill in the art will appreciate that platforms may be configured to have an outboard surface that is slight curved and convex, with the curvature corresponding to the circumference of the turbine at the radial location of the rotor blades. As used herein, this type of platform shape is deemed planar, as the radius of curvature is sufficiently great to give the platform a flat appearance.) More specifically, the platform110may have a planar topside113, which, as shown inFIG. 1, may include an axially and circumferentially extending flat surface. As shown inFIG. 2, the platform110may have a planar underside114, which may also include an axially and circumferentially extending flat surface. The topside113and the bottom side114of the platform110may be formed such that each is substantially parallel to the other. As depicted, it will be appreciated that the platform110typically has a thin radial profile, i.e., there is a relatively short radial distance between the topside113and the bottom side114of the platform110.

In general, the platform110is employed on turbine rotor blades100to form the inner flow path boundary of the hot gas path section of the gas turbine. The platform110further provides structural support for the airfoil102. In operation, the rotational velocity of the turbine induces mechanical loading that creates highly stressed regions along the platform110that, when coupled with high temperatures, ultimately cause the formation of operational defects, such as oxidation, creep, low-cycle fatigue cracking, and others. These defects, of course, negatively impact the useful life of the rotor blade100. It will be appreciated that these harsh operating conditions, i.e., exposure to extreme temperatures of the hot gas path and mechanical loading associated with the rotating blades, create considerable challenges in designing durable, long-lasting rotor blade platforms110that both perform well and are cost-effective to manufacture.

One common solution to make the platform region110more durable is to cool it with a flow of compressed air or other coolant during operation, and a variety of these type of platform designs are known. However, as one of ordinary skill in the art will appreciate, the platform region110presents certain design challenges that make it difficult to cool in this manner. In significant part, this is due to the awkward geometry of this region, in that, as described, the platform110is a periphery component that resides away from the central core of the rotor blade and typically is designed to have a structurally sound, but thin radial thickness.

To circulate coolant, rotor blades100typically include one or more hollow interior cooling passages116(seeFIGS. 3,4and5) that extend radially through the interior of the blade100, including through the root104and the airfoil102. As described in more detail below, to increase the exchange of heat, such interior cooling passages116may be formed having a serpentine path that winds through the central regions of the blade100, though other configurations are possible. In operation, a coolant may enter the interior cooling passage via one or more inlets117formed in the inboard surface of the dovetail109. The coolant may circulate through the blade100and exit through outlets (not shown) formed on the airfoil and/or via one or more outlets (not shown) formed in the root104. The coolant may be pressurized, and, for example, may include pressurized air, pressurized air mixed with water, steam, and the like. In many cases, the coolant is compressed air that is diverted from the compressor of the engine, though other sources are possible. As discussed in more detail below, these interior cooling passages typically include a high-pressure coolant region and a low-pressure coolant region. The high-pressure coolant region typically corresponds to an upstream portion of the cooling passage that has a higher coolant pressure, whereas the low-pressure coolant region corresponds to a downstream portion having a relatively lower coolant pressure.

In some cases, the coolant may be directed from the interior cooling passages116into a cavity119formed between the shanks112and platforms110of adjacent rotor blades100. From there, the coolant may be used to cool the platform region110of the blade, a conventional design of which is presented inFIG. 3. This type of design typically extracts air from one of the interior cooling passages116and uses the air to pressurize the cavity119formed between the shanks112/platforms110. Once pressurized, this cavity119then supplies coolant to cooling channels that extend through the platforms110. After traversing the platform110, the cooling air may exit the cavity through film cooling holes formed in the topside113of the platform110.

It will be appreciated, however, that this type of conventional design has several disadvantages. First, the cooling circuit is not self-contained in one part, as the cooling circuit is only formed after two neighboring rotor blades100are assembled. This adds a great degree of difficulty and complexity to installation and pre-installation flow testing. A second disadvantage is that the integrity of the cavity119formed between adjacent rotor blades100is dependent on how well the perimeter of the cavity119is sealed. Inadequate sealing may result in inadequate platform cooling and/or wasted cooling air. A third disadvantage is the inherent risk that hot gas path gases may be ingested into the cavity119or the platform itself110. This may occur if the cavity119is not maintained at a sufficiently high pressure during operation. If the pressure of the cavity119falls below the pressure within the hot gas path, hot gases will be ingested into the shank cavity119or the platform110itself, which typically damages these components as they were not designed to endure exposure to the hot gas-path conditions.

FIGS. 4 and 5illustrate another type of conventional design for platform cooling. In this case, the cooling circuit is contained within the rotor blade100and does not involve the shank cavity119, as depicted. Cooling air is extracted from one of the interior cooling passages116that extend through the core of the blade100and directed aft through cooling channels formed within the platform110(i.e., “platform cooling channels120”). As shown by the several arrows, the cooling air flows through the platform cooling channels120and exits through outlets in the aft edge121of the platform110or from outlets disposed along the suction side edge122. (Note that in describing or referring to the edges or faces of the rectangular platform110, each may be delineated based upon its location in relation to the suction face105and pressure face106of the airfoil102and/or the forward and aft directions of the engine once the blade100is installed. As such, as one of ordinary skill in the art will appreciate, the platform may include an aft edge121, a suction side edge122, a forward edge124, and a pressure side edge126, as indicated inFIGS. 3 and 4. In addition, the suction side edge122and the pressure side edge126also are commonly referred to as “slashfaces” and the narrow cavity formed therebetween once neighboring rotor blades100are installed may be referred to as a “slashface cavity”.)

It will be appreciated that the conventional designs ofFIGS. 4 and 5have an advantage over the design ofFIG. 3in that they are not affected by variations in assembly or installation conditions. However, conventional designs of this nature have several limitations or drawbacks. First, as illustrated, only a single circuit is provided on each side of the airfoil102and, thus, there is the disadvantage of having limited control of the amount of cooling air used at different locations in the platform110. Second, conventional designs of this type have a coverage area that is generally limited. While the serpentine path ofFIG. 5is an improvement in terms of coverage overFIG. 4, there are still dead areas within the platform110that remain uncooled. Third, to obtain better coverage with intricately formed platform cooling channels120, manufacturing costs increase dramatically, particularly if the cooling channels having shapes that require a casting process to form. Fourth, these conventional designs typically dump coolant into the hot gas path after usage and before the coolant is completely exhausted, which negatively affects the efficiency of the engine. Fifth, conventional designs of this nature generally have little flexibility. That is, the channels120are formed as an integral part of the platform110and provide little or no opportunity to change their function or configuration as operating conditions vary. These types of conventional designs are difficult to repair or refurbish.

In addition, as one of ordinary skill in the art will appreciate, another challenge associated with these types of cooling arrangements is connecting the platform cooling circuit, i.e., the interior cooling passages formed through the interior of the platform to the main cooling circuit, i.e., the interior cooling passages formed through the interior of the root and airfoil. One reason for this is that the connection required typically must be formed through a high-stress region of the blade. Another relates to the advantages associated with having the core of the platform cooling circuit remain unconnected to the core of the main cooling circuit during the casting process. For example, typically the platform cooling circuit has tight tolerance requirements associated with the placement of the interior cooling passages in relation to the outer surface of the platform. Because of its length, the core of the main cooling circuit is apt to move when the mold is filled during the casting process. This movement, while acceptable for the placement of the main cooling circuit, makes it difficult to satisfy the tight placement tolerances of the platform cooling circuit if the movement of the main core is translated to the platform core. Having the two cores remain unconnected through the casting process means the movement of the main core does not affect the ultimate placement of the platform cooling circuit. Of course, this requires that a post-cast connection be made. Being a region of high stress, this connection must be formed such that structural integrity is maintained.

Conventional platform cooling designs fail to satisfy these important requirements. There remains a need for improved apparatus, systems, and methods that effectively cool the platform region of turbine rotor blades in an efficient manner, while also being cost-effective to construct, flexible in application, structurally sound, and durable.

BRIEF DESCRIPTION OF THE INVENTION

The present application thus describe a configuration of cooling channels through the interior of a turbine rotor blade, the turbine rotor blade including a platform at an interface between an airfoil and a root. In one embodiment, the configuration of cooling channels includes: an interior cooling passage that is configured to extend from a connection with a coolant source in the root to the interior of the airfoil; a platform cooling channel that traverses at least a portion of the platform; a turndown extension that includes a first section, which comprises a connection with the platform cooling channel, and a second section, which comprises a radially oriented cooling channel; and a connector that extends from a connector opening formed through an outer face of the root to a connection with the interior cooling passage and, therebetween, bisects the second section of the turndown extension.

A method of manufacturing a configuration of cooling channels through the interior of a turbine rotor blade, the turbine rotor blade having a platform at an interface between an airfoil and a root. In one embodiment, the method includes the steps of: forming an interior cooling passage that is configured to extend from a connection with a coolant source in the root to the interior of the airfoil; forming a platform cooling channel that traverses at least a portion of the platform; forming a turndown extension that comprises a first section, which forms a connection with the platform cooling channel, and a second section, which comprises a radially oriented cooling channel; and forming a connector that extends from an opening formed through an outer face of the root to a connection with the interior cooling passage and, therebetween, bisects the second section of the turndown extension.

These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

It will be appreciated that turbine blades that are cooled via the internal circulation of a coolant typically include main or interior cooling passage that extends radially outward from the root, through the platform region, and into the airfoil, as described above in relation to several conventional cooling designs. It will be appreciated that certain embodiments of the present invention may be used in conjunction with such interior cooling passages to enhance or enable efficient active platform cooling, and the present invention is discussed in connection with a common design: an interior cooling passage116having a winding or serpentine configuration. As depicted inFIG. 6, the serpentine path is typically configured to allow a one-way flow of coolant and includes features that promote the exchange of heat between the coolant and the surrounding rotor blade100. In operation, a pressurized coolant, which typically is compressed air bled from the compressor (though other types of coolant, such as steam, also may be used with embodiments of the present invention), is supplied to the interior cooling passage116through a connection formed through the root104. The pressure drives the coolant through the interior cooling passage116, and the coolant convects heat from the surrounding walls.

As the coolant moves through the interior cooling passage116, it will be appreciated that it loses pressure, with the coolant in the upstream portions of the interior cooling passage116having a higher pressure than coolant in downstream portions. As discussed in more detail below, in some embodiments of the present invention, this pressure differential may be used to drive coolant across or through interior cooling passages formed in the platform. It will be appreciated that the present invention may be used in rotor blades100having internal interior cooling passages of different configurations and is not limited to interior cooling passages having a serpentine form. Accordingly, as used herein, the term “interior cooling passage” or “cooling passage” is meant to include any passage or hollow channel through which coolant may be circulated in the rotor blade. As provided herein, the interior cooling passage116of the present invention extends to at least to the approximate radial height of the platform116, and may include at least one region of relatively higher coolant pressure (which, hereinafter, is referred to as a “region of high pressure” and, in some cases, may be an upstream section within a serpentine passage) and at least one region of relatively lower coolant pressure (which, hereinafter, is referred to as a “region of low pressure” and, relative to the region of high pressure, may be a downstream section within a serpentine passage).

In general, the various designs of conventional internal interior cooling passages116are effective at providing active cooling to certain regions within the rotor blade100. However, as one of ordinary skill in the art will appreciate, the platform region proves more challenging. This is due, at least in part, to the platform's awkward geometry—i.e., its narrow radial height and the manner in which it juts away from the core or main body of the rotor blade100. However, given its exposures to the extreme temperatures of hot gas path and high mechanical loading, the cooling requirements of the platform are considerable. As described above, conventional platform cooling designs are ineffective because they fail to address the particular challenges of the region, are inefficient with their usage of coolant, and/or are costly to fabricate.

Referring again to the figures,FIGS. 6 through 9provide several views of exemplary embodiments of the present invention. As shown, the present invention generally includes a configuration of cooling channels through the interior of a turbine rotor blade100. The turbine rotor blade may include a platform110at an interface between an airfoil102and a root104. The configuration may include an interior cooling passage116that is configured to extend from a connection with a coolant source that is made through the root104to the interior of the airfoil102, a platform cooling channel132that traverses at least a portion of the platform. As shown, the platform cooling channel132may have a serpentine form, though other configurations are possible. The present invention may further included a turndown extension134that includes a first section136, which comprises a connection with the platform cooling channel132, and a second section138, which comprises a radially oriented cooling channel. The present invention may further include a connector140that extends from a connector opening142formed through an outer face of the root104to a connection with the interior cooling passage116and, therebetween, bisects the second section138of the turndown extension134, as shown.

As stated, the root104may include means for connecting it to the rotor wheel, which typically include a dovetail109and a shank112. The connector opening142may be formed through the outer face of the shank. The connector opening142may be located just inboard of the platform110. In some embodiments, the connector opening142is located in a fillet region formed in the shank that resides just inboard of the platform. As shown, the connector opening142may include a plug144. The plug144may be formed to completely block the connector opening142. From the connector opening142, the connector140may extend diagonally in an outboard direction. At an inner radial end of the second section138of the turndown extension134, the turndown extension134may have a dead-end146.

The platform110may have a planar configuration. The longitudinal axis of the platform cooling channel132may have an approximate parallel relationship with the plane of the platform110. The first section136of the turndown extension134may have an axially/circumferentially oriented cooling channel (i.e., be approximately perpendicular to a radially oriented reference line). The first section136may be approximately parallel to the platform cooling channel132to which it connects. From the first section136, the turndown extension134may have an approximate 90° elbow transition between the first section136and the second section138.

The connector140may be configured such that it obliquely bisects the second section138of the turndown extension134, and the cross-sectional shape of the connector140may be circular. In this manner, the obliquely bisecting connector140forms wall openings in the second section138that have an elliptical shape. It will be appreciated that this intersection is located in a region that is typically prone to high radial stresses. With the radially oriented major-axis, the elliptical inlet geometry mitigates these typical stress concentrations that arise when creating machined connections between such cores. As indicated inFIG. 7, the connector140may be linear and have a longitudinal axis152. The second section138of the turndown extension134may also be linear in shape and have a longitudinal axis154.

As stated, the connector140may obliquely bisect the second section138, which may form an acute angle156, as shown. It has been determined that if the acute angle156falls within certain dimensional ranges performance advantages will be realized. In a preferred embodiment, the acute angle formed between the longitudinal axis152of the connector140and the longitudinal axis154of the second section138of the turndown extension134falls within the range of between 15° and 75°. More preferable, the acute angle156formed between the longitudinal axis152of the connector140and the longitudinal axis154of the second section138of the turndown extension134is between 30° and 60°. More preferable still, the acute angle156formed between the longitudinal axis152of the connector140and the longitudinal axis154of the second section138of the turndown extension134is approximately 45°.

As stated, the second section138may be configured such that it has an approximate radial orientation. In a preferred embodiment, the longitudinal axis154of the second section138forms an acute angle with a radially oriented reference line of between 30° and −30°. More preferable, the second section138is configured such that the longitudinal axis154of the second section138forms an acute angle with a radially oriented reference line of between 10° and −10°.

In one preferred embodiment, as shown inFIG. 6, the interior cooling passage116may be configured such that, in operation, it includes a high-pressure coolant region (or area of relatively higher pressure) and a low-pressure coolant region (or area of relatively lower pressure). In this case, the platform cooling channel132may include an upstream end160and a downstream end162, each of which includes a turndown extension134positioned in proximity to it. Accordingly, an upstream turndown extension134may include a first section136that forms a connection with the upstream end160of the platform cooling channel132; and a downstream turndown extension134may include a first section136that forms a connection with the downstream end162of the platform cooling channel132. A connector140may be formed at each of the turndown extensions134: a high-pressure connector140and a low-pressure connector140. The high-pressure connector140may extend from a connector opening142formed through an outer face of the shank112to a connection with the high-pressure coolant region of the interior cooling passage116; therebetween, the high-pressure connector140may bisect the second section138of the upstream turndown extension134. The low-pressure connector140may extend from a connector opening142formed through an outer face of the shank112to a connection with the low-pressure coolant region of the interior cooling passage116; therebetween, the low-pressure connector140may bisect the second section138of the downstream turndown extension134. The connector openings142may be plugged such that coolant is prevented from exiting at that location. In use, it will be appreciated that the pressure differential between the high-pressure connector140and the low-pressure connector140may drive coolant across the platform cooling channel132and through whatever heat exchanging structure it includes.

In one embodiment, the platform cooling channel132takes a serpentine form, as illustrated inFIG. 6. As stated above, the airfoil102includes a pressure face106and a suction face105. A pressure side of the platform is the side of the platform110that corresponds with the pressure side106of the airfoil102, and the pressure side slashface126may be the linear edge of the pressure side of the platform110. In a preferred embodiment, the platform cooling channel132may be located primarily through the interior of the pressure side of the platform, as depicted inFIG. 6. In addition, in relation to the forward and aft directions of the turbine rotor blade100, the upstream end160of the platform cooling channel132may have a forward position and the downstream end162of the channel132may have an aft position.

In a preferred embodiment, as illustrated inFIG. 6, the platform cooling channel132may have a slashface section164. The slashface section164may be a section of the platform cooling channel132that resides in proximity and parallel to the pressure side slashface126along a majority of the length of the pressure side slashface126. The upstream end of the slashface section164may reside in proximity to the upstream end of the platform cooling channel132. It will be appreciated that this configuration, i.e., the positioning of the slashface section164in proximity to the upstream end160of the platform cooling channel132, allows this section to receive coolant having the lowest temperature (relative to the other sections of the platform cooling channel132). As the pressure side slashface126is an area having particularly high cooling requirements, this configuration provides performance advantages. From the slashface section164, the platform cooling channel132comprises a first switchback166and, downstream of the first switchback166, an internal section168that resides in the central area of the pressure side of the platform. As shown, the internal section168may include a linear section170immediately downstream of the first switchback168, and a second switchback downstream of the linear section170. The second switchback may reside in proximity to the downstream end162of the platform cooling channel132.

In some embodiments, the upstream turndown extension134may have a forward position along the pressure side junction between the platform110and the shank112. Relative to the upstream turndown extension134, the downstream turndown extension134may have an aft position along the pressure side junction between the platform110and the shank112. It will be appreciated that, being positioned along the junction of the platform110and the shank112, allows that the connection between the second section138of the turndown extension134and the interior cooling passage116be made via a connector140having a relatively short length.

As illustrated inFIG. 8, according to the present invention, the platform cooling channel132may be configured having certain cross-sectional shape and dimensions that increase heat transfer between the platform and a coolant flowing therethrough. In a preferred embodiment, the platform cooling channel132may be substantially rectangular in shape, as indicated inFIG. 8. Fillet regions may be present in the corners of the cross-sectional rectangular shape to reduce stress concentrations and give it an almost oval appearance. The rectangular shape may be configured to have a height176in the radial direction and a width178in the axial/circumferential directions. In a preferred embodiment, the platform cooling channel132may be configured such that the width178is greater than the height176. This may be the case for the entire length of the platform cooling channel132or may be applied to the majority of the length. In another preferred embodiment, the platform cooling channel132may be configured such that the width178is at least greater than twice the height176. This also may be the case for the entire length of the platform cooling channel132or may be applied to the majority of the length. It will be appreciated that, given the planar shape of the platform region, configurations having a greater width178increase the available surface area through the platform cooling channel132, which increases the exchange of heat between the surrounding platform110and a coolant flowing through the cooling channel132.

FIG. 6illustrates another aspect of the present invention. In some preferred embodiments, one or more cooling apertures179may be provided. The cooling apertures179, as shown, may include small channels that, during operation, releases a desired portion of the coolant flowing through the platform cooling channel132from outlets or cooling apertures179formed on the platform110. As shown, the cooling apertures179, in preferred embodiments, are located on the pressure side slashface126or the topside113of the platform110. In regard to the cooling apertures179located on the pressure side slashface126, the cooling apertures179may be narrow so that the released coolant is impinged and directed with velocity against the slashface of the adjacent turbine blade100, which generally increases its cooling effectiveness. It will be appreciated that the slashface cavity and the slashfaces that define them are difficult regions of the platform110to cool, and that cooling apertures179may be an effective way to do this. The cooling apertures179may be sized such that a desired and/or metered flow is achieved.

The present invention further includes a novel method for efficiently forming effective interior cooling channels within the platform region of turbine rotor blades. More specifically, the present invention includes a method of manufacturing a configuration of cooling channels through the interior of a turbine rotor blade. The turbine rotor blade100may have a platform110at an interface between an airfoil102and a root104. In one preferred embodiments, the method may include the steps of: forming an interior cooling passage116that is configured to extend from a connection with a coolant source in the root104to the interior of the airfoil102; forming a platform cooling channel132that traverses at least a portion of the platform110; forming a turndown extension134that comprises a first section136, which forms a connection with the platform cooling channel132, and a second section138, which comprises a radially oriented cooling channel; and forming a connector140that extends from a connector opening142formed through an outer face of the root104to a connection with the interior cooling passage116and, therebetween, bisects the second section138of the turndown extension134. The forming of the turndown extension134may include a casting process. A casting process may also be used to form the interior cooling passage116and the platform cooling channels132. The core used to form the interior cooling passage116and the core used to form both the platform cooling channels132may be unconnected while being formed by the casting process, which, as stated above, may be advantageous. The connector140then may be formed after the turndown extension134and interior cooling passage116is formed.

Given the possible configurations discussed, the forming the connector140may be completed with a relatively uncomplicated and cost-effective line-of-sight machining process. In one preferred embodiment, as shown inFIG. 7, a guide rod180may be positioned during the casting process that serves to guide the post-cast machining, which may be a mechanical drilling process, of the connector140. It will be appreciated that the dashed lines inFIG. 7represent the ultimate configuration of the connector140once the machining process is completed. Given this geometry, the connector140may be efficiently formed with a single pull plane machining operation. A plug144may be installed to complete the cooling channel configuration. The plug144may be installed within the connector opening142using conventional methods, such as through mechanical interference, welding, brazing, etc. It will be appreciated that these several steps may be used to create the several alternative embodiments discussed above.

In operation, according to an exemplary embodiment of the present application, a coolant may enter the interior cooling passage116through a forward area of the dovetail109and, after being directed into the airfoil102, flow radially outward/inward through a serpentine-configured interior cooling passage116as the coolant meanders in an aftwise direction. As shown, the high-pressure connector140may be configured such that an upstream (and higher pressure) portion of the interior cooling passage116fluidly communicates with an upstream turndown extension134, which then directs the coolant into the upstream end160of the platform cooling channel132. The low-pressure connector140may be configured such that a downstream (and lower pressure) portion of the interior cooling passage116fluidly communicates with a downstream turndown extension134. The downstream turndown extension134may collect coolant exiting the platform cooling channel132and return the coolant to the interior cooling passage116, where the coolant may be used in other downstream cooling applications and/or exhausted through cooling apertures located elsewhere on the rotor blade.

In this manner, the platform cooling arrangement of the present invention may extracts a portion of the coolant from the interior cooling passage116, use the coolant to remove heat from the platform110, and then return the coolant to the interior cooling passage116, where the coolant may be used further. It will be appreciated that the present invention accomplishes this while being efficient and cost-effective to manufacture, and while maintaining the structural integrity of the rotor blade. The separation of the platform core and the main core during the casting process, according to certain preferred embodiments described above, provide other performance advantages and efficiencies during the casting process.

As one of ordinary skill in the art will appreciate, the many varying features and configurations described above in relation to the several exemplary embodiments may be further selectively applied to form the other possible embodiments of the present invention. For the sake of brevity and taking into account the abilities of one of ordinary skill in the art, all of the possible iterations is not provided or discussed in detail, though all combinations and possible embodiments embraced by the several claims below or otherwise are intended to be part of the instant application. In addition, from the above description of several exemplary embodiments of the invention, those skilled in the art will perceive improvements, changes, and modifications. Such improvements, changes, and modifications within the skill of the art are also intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.