Vapor cooled static turbine hardware

A cooling system for a gas turbine engine includes a non-rotating component extending into an engine flowpath, a vapor cooling assembly configured to transport thermal energy from a vaporization section to a condenser section through cyclical evaporation and condensation of a working medium sealed within the vapor cooling assembly, wherein the vaporization section is located at least partially within the non-rotating component, and wherein the condenser section is located outside the non-rotating component and away from the engine flowpath.

BACKGROUND OF THE INVENTION

The present invention relates to a system for cooling static structures of gas turbine engines.

Known gas turbine engines have utilized superalloys, thermal barrier coatings (TBCs), and fluidic cooling schemes in order to provide engine structures that can operate efficiently at high temperatures and pressures while still maintaining a relatively long lifespan. However, it is desired to provide improved cooling capabilities for gas turbine engines, in order to better maintain engine components at temperatures below designated maximum operating temperature levels. Moreover, it is desired to reduce energy losses by permitting thrust recovery of thermal energy transferred away from a gas flowpath by a cooling system.

BRIEF SUMMARY OF THE INVENTION

A cooling system for a gas turbine engine according to the present invention includes a non-rotating component extending into an engine flowpath, a vapor cooling assembly configured to transport thermal energy from a vaporization section to a condenser section through cyclical evaporation and condensation of a working medium sealed within the vapor cooling assembly, wherein the vaporization section is located at least partially within the non-rotating component, and wherein the condenser section is located outside the non-rotating component and away from the engine flowpath.

DETAILED DESCRIPTION

In general, the present invention relates to a gas turbine engine that utilizes a vapor cooling assembly to cool non-rotating structures that extend into a gas flowpath (typically a combustion or turbine flowpath). The vapor cooling assembly includes a vaporization section located at least partially within a static structure that is exposed to a gas flowpath from which it is desired to remove thermal energy, and a condenser section located adjacent to or spaced from the gas flowpath where it is desired to expel thermal energy. The vapor cooling assembly is configured to transport thermal energy from the vaporization section to the condenser section at a relatively high rate through cyclical evaporation and condensation of a working medium sealed within the vapor cooling assembly. The condenser section can expel thermal energy to a fan bypass stream located adjacent to the combustion gas flowpath, in order to permit thrust recovery of that thermal energy in the fan bypass stream. A flow guide structure can be used to direct fan bypass air toward and past the condenser section.

As used herein, the term “static” as applied to gas turbine engine parts generally refers to non-rotating parts, although such parts may be subject to some movement, for instance, when installed in an engine of a movable vehicle.

FIG. 1is a schematic view of a dual-spool gas turbine engine10that includes a fan section12, a low-pressure compressor section14, a high-pressure compressor section16, a combustor section18, a high-pressure turbine section20, a low-pressure turbine section22, and a fan bypass duct24. A centerline CL is defined by the engine10. The illustrated embodiment of the gas turbine engine10is provided merely by way of example, and it should be recognized that the present invention applies to gas turbine engines of any configuration. Those of ordinary skill in the art will understand the basic operation of gas turbine engines, and therefore further discussion here is unnecessary.

The engine10further includes a vapor cooling assembly26located at the low-pressure turbine section22.FIG. 2is an enlarged schematic view of a portion of the gas turbine engine10, showing the vapor cooling assembly26in greater detail. As shown inFIG. 2, a gas flowpath (e.g., combustion of turbine flowpath) is defined between a first boundary wall28and a second boundary wall30. A fan bypass flowpath is defined by the fan bypass duct24. Gas in the fan bypass flowpath is generally at a lower temperature and pressure than gas in the combustion gas flowpath. The illustrated embodiment of the engine10shows the second boundary wall30forming a boundary of both the combustion gas flowpath and the fan bypass duct24. However, the combustion gas flowpath and the bypass duct24can be spaced apart in alternative embodiments.

An airfoil-shaped vane32of a stator assembly at the low-pressure turbine section22extends into the combustion flowpath. The vane32is a static component of the gas turbine engine10. In an alternative embodiment, the structure designated by reference number32inFIG. 2could represent a strut.

The vapor cooling assembly26includes a vaporization section34that extends into the vane32and a condenser section36that is located away from the combustion gas flowpath. The condenser section36extends either fully or at least partially into the fan bypass duct24(or other suitable area, e.g., one in which the vapor can be cooled) and an optional flow guide38directs fan bypass air toward and along the condenser section36. Air passing along the condenser section36absorbs thermal energy expelled from the vapor cooling assembly26. It should be recognized that the particular size and shape of the vaporization section34, and its particular location within the vane32can vary as desired. Likewise, the particular configuration of the condenser section36can vary as desired.

The engine10includes a plurality of vanes arranged in an annular configuration about the centerline CL. In one embodiment, each vane of a particular stage is configured like vane32, as shown inFIG. 2. That is, each vane32has a dedicated vapor cooling assembly26, and a number of discrete condenser sections36extend into the fan bypass duct24. In alternative embodiments, the vapor cooling assembly26provides cooling to a number of different structures of the engine10. For example, nozzle segments that each include two or more airfoil shaped vanes could utilize a common, shared condenser section36with separate vaporization sections34that extend into each vane32of the nozzle.

The vapor cooling assembly26is sealed, and contains a working medium. The vapor cooling assembly26functions as a heat pipe that uses an evaporative cooling cycle to transfer thermal energy through the evaporation and condensation of a working medium. In particular, the vapor cooling assembly26utilizes an evaporative cooling cycle to transfer thermal energy from the vane32to air passing through the fan bypass duct24. Thermal energy absorbed by the vane32from the hot gases in the combustion gas flowpath heats the vaporization section34, which causes the working medium in the vaporization section34to evaporate. Moreover, the relatively cool air in the fan bypass flowpath absorbs thermal energy from the condenser section36, and causes the (vaporized) working medium to condense. The working medium physically moves between the vaporization section34and the condenser section36, in order to transfer the thermal energy between the locations where evaporation and condensation occur. Conventional capillary action structures (e.g., wicking structures) or a capillary action foam are included inside the vapor cooling assembly26in order to facilitate desired movement of the working medium along an established path between the condenser section36and the vaporization section34in a well-known manner without requiring the aid of gravity or other orientation-specific limits.

The composition of the working medium used in the vapor cooling assembly26is selected according to the particular operating conditions at which heat transfer is desired. Typically, working media conventionally used with evaporative cooling cycles are dependent upon operation within a particular range of temperature conditions (as well as pressure conditions). It is therefore necessary to select a suitable working medium based on the particular conditions under which each of the vapor cooling assembly is expected to operate, as will be understood by those skilled in the art. Temperatures in typical gas turbine engines can reach 1,649° C. (3,000° F.) or more, although actual engine temperatures will vary for different applications, and under different operating conditions. For instance, while the vapor cooling assembly26is operational, the engine10is configured such that the average gas flowpath temperature in will generally not exceed the maximum temperature limits for the materials (e.g., metals and ceramics) used in and along the combustion gas flowpath. A non-exclusive list of possible working media is provided in Table 1, although those skilled in the art will recognize that other working medium materials can be used.

The optional flow guide38functions to direct air in the fan bypass flowpath toward and past the condenser section36of the vapor cooling assembly26, and can then direct air heated by the condenser section36back to the fan bypass flowpath. The flow guide38can be configured similarly to flow guides used in conjunction with known heat exchangers. As shown inFIG. 2, the condenser section36is represented schematically as a box within the throat of the flow guide38. However, it should be recognized that various embodiments of the present invention can incorporate a condenser section36configured with fins or other structures that span the throat of the flow guide38, and have slots or passageways for air to flow between those fins or other structures.

The vapor cooling assembly26can provide cooling to static components of the engine10, such as the vane32, with essentially zero net energy loss, because the thermal energy transferred away from the combustion gas flowpath by the vapor cooling assembly26is as air in the fan bypass flowpath gains thermal energy. Thermal energy added to air in the fan bypass flowpath raises the temperature and pressure of that air, which contributes to thrust output of the engine10. The flow guide38promotes efficient flow of air along the condenser section36, and helps prevent aerodynamic efficiency losses in the fan bypass duct24.

The use of the vapor cooling assembly26of the present invention does not require the use of bleed air to achieve cooling of static engine components. The use of bleed air in prior art cooling system produces significant engine efficiency losses (e.g., in terms of thrust output or fuel burn efficiency). In that respect, the present invention provides a more efficient cooling system.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For instance, the system of the present invention can be used to cool nearly any static component in nearly any location of a gas turbine engine.