Gas turbine engine with air and fuel cooling system

A gas turbine engine is provided with a first heat exchanger associated with a cooling air flow to deliver cooling air to a turbine section. A second heat exchanger is associated with a fuel supply line for delivering fuel into a combustion section. An intermediate fluid cools air at the first heat exchanger and heats fuel at the second heat exchanger.

BACKGROUND OF THE INVENTION

This application relates to a cooling system for cooling air in a gas turbine engine by heating fuel, and wherein an intermediate fluid is utilized to perform the heat exchange.

Gas turbine engines are known, and typically include a compressor for compressing air and delivering it downstream into a combustion section. The compressed air is mixed with fuel and combusted in the combustion section. The products of this combustion are then delivered downstream over turbine rotors which are driven to rotate, to provide power to the engine.

The turbine rotors are subjected to very high temperatures by the products of combustion. Thus, it is known to tap cooling air and deliver that cooling air to components of the turbine section to cool those components.

However, competing with this use of air is the goal to provide higher pressure ratios at the compressor for improved combustion. As the pressure ratios increase, so does the air temperature. Thus, the air downstream of the compressor is less useful as cooling air since it becomes hotter to provide the higher pressure ratios.

It has been proposed to cool the air downstream of the compressor by exchanging heat in the air to fuel being delivered into the combustion section. Generally, this has been performed by placing the air and fuel in close heat exchange relationship.

This is somewhat undesirable, in that having quantities of cooling air in the vicinity of the fuel makes any air or fuel leakage more risky.

SUMMARY OF THE INVENTION

In the disclosed embodiment of this invention, an intermediate fluid cools air which is to be utilized as cooling air and transfers heat to the fuel at a location adjacent to the combustion section. In disclosed embodiments, the exchanger for cooling the air may be in a plenum for delivering the cooling air to turbine sections. In one embodiment, the intermediate fluid is provided by a heat pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A gas turbine engine10, such as a turbofan gas turbine engine, circumferentially disposed about an engine centerline, or axial centerline axis12is shown inFIG. 1. The engine10includes a fan11, compressors13, a combustion section14, and a turbine section15. As is well known in the art, air compressed in the compressors13is mixed with fuel and burned in the combustion section14, and expanded across turbine rotors. The turbine rotors include blades20and static airfoils or vanes19. This structure is shown somewhat schematically inFIG. 1. It should be understood that this application extends to other types of gas turbine engines for any application.

As shown inFIG. 2, a system for heating fuel being delivered through fuel nozzle/spray bars50into a combustion chamber51is provided by a heat exchanger52associated with the fuel nozzle/spray bar50. The heat exchanger52communicates through a heat pipe54with the interior of a cooling air plenum56. A heat exchanger58is positioned within the plenum56, and will cool air being delivered to cool a static vane60. A similar plenum62is provided with heat exchanger64and a heat pipe66. Yet another heat pipe68communicates into a plenum70and to a heat exchanger72. Plenum70may be for delivering cooling air to an inner peripheral chamber74to cool a turbine blade75. An intermediate fluid flowing through the heat pipes cools the air across the heat exchangers58,64and72at a location adjacent the use of this cooling air. There is now less chance for this cooling air to mix with fuel at the combustion section. Moreover, the fuel is heated in the heat exchanger52, at the combustion section, and there is little chance for fuel leakage causing any concerns.

As known, a heat pipe generally includes a porous medium which wicks a liquid by capillary action from a cool source, here the interior of heat exchanger52, toward a hot source, here the interior of air heat exchangers58,64and72. As the liquid reaches the heat exchanger58,64and72, it is vaporized by hot air flowing across the heat exchangers, absorbing the heat. This cools the air. This vaporized fluid then expands back through channels in the porous medium of the heat pipes toward the cool source, or heat exchanger52where it is again condensed by cool fuel flowing across heat exchanger52. This is a continuous action driven by the difference in temperature. Heat pipes are well known technology, however, they have not been utilized in this particular application. The use of intermediate fluid, and in the disclosed embodiment heat pipes, allows the air to be cooled where it is to be utilized while heating the fuel adjacent to where it will be burned.

It should be understood that several sets of the heat exchangers and heat pipes may be positioned circumferentially spaced about axis12.

While an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. As an example, intermediate fluids other than in a heat pipe may be used. For that reason, the following claims should be studied to determine the true scope and content of this invention.