JPH0467568B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION This invention relates to a turbine cooling air system for use in a gas turbine engine.

BACKGROUND OF THE INVENTION As turbine inlet temperatures increase to improve the efficiency of gas turbine engines, turbine blades and It became necessary to supply cooling air to the stator blades. At higher operating temperatures, such as during takeoff when the engine is used to power the aircraft, the amount of cooling air required is relatively large. In contrast, at lower temperature operating conditions, such as idling, relatively little, if any, cooling air is required for the turbine components. Despite these very different operating conditions, it has not generally been considered desirable to modulate the flow of cooling air to turbine components for reasons of simplicity and safety. . As a result, since the engine must be designed to provide the required amount of cooling air flow during the hottest conditions, an excess amount of cooling air may be provided during other operating conditions and during these periods of operation. while,
It tends to reduce the efficiency of the institution. Excessive flow under these conditions is wasteful and results in poor performance.
More fuel is consumed than if this flow rate were reduced to the minimum amount required for each particular operating condition.

In response to this efficiency problem, various ideas have been proposed and explored for controlling or modulating the turbine cooling flow to eliminate unnecessary performance losses. Typically, the device consists of a flow modulating valve or device located somewhere within the flow chain from source to suction. Many devices are very complex, employing a large number of moving parts located essentially within the engine, and are therefore relatively inaccessible for inspection, adjustment, or repair. Many of these complex devices often have to operate in hot, hard-to-access areas where it may be difficult or impossible to lubricate or maintain parts, especially if they are susceptible to unreliable conditions such as sticking or jamming. There are also gender issues.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved modulated cooling system for a gas turbine engine.

Another object of the invention is to provide an improved cooling system for a gas turbine engine that includes a modulator having an external actuator that is easy to access and service.

Another object of the invention is to provide an improved cooling flow modulation cooling system for a gas turbine engine using a structurally uncomplicated form that avoids excessive pressure losses.

The above and other objects and features of the present invention will become readily apparent from the following description.

SUMMARY OF THE INVENTION In one embodiment of the invention, a cooling airflow modulator includes a circumferential manifold that collects and sources high pressure cooling air for a rotating turbine portion of an engine. Modulation of the cooling airflow to the turbine section is accomplished by modulating the source of compressor discharge air flowing into the circumferential manifold. The compressor discharge air has one or more inlet ports located close to the compressed air outlet so that the compressed air exiting the compressor section can flow continuously into those passages. Physically directed into many local passageways. These passages are configured to direct relatively cool compressor discharge air radially inward and then axially downstream to the manifold location. Valve means are provided near the inlet ports of the one or more passageways to modulate the flow rate of cooling air through those passageways. This modulation controls the supply of air to the manifold. The valve means is actuated in response to engine operating conditions to provide an appropriate amount of cooling air flow to the engine turbine blades during changing engine operating conditions.

Although the gist of this invention is clearly and specifically described in the claims, it is believed that this invention will be clearly understood from the following description of the drawings.

DESCRIPTION OF THE EMBODIMENTS Referring to FIG. 1, a gas turbine engine portion 10 has a compressor 12, a combustor 14, a high pressure turbine 16, and a low pressure turbine 18 arranged in flow series. In normal operation, after compressor 12 pressurizes the inlet air, the air passes entirely to the combustor 14 region. A large portion of this compressed air enters the combustor 14 where it is mixed with fuel and ignited to form a hot, high pressure gas that flows into the high pressure turbine 16 to rotate the individual turbine blades 20. , thus providing a means for transmitting mechanical power to the compressor 12 via the shaft 22. The high-pressure turbine discharges this gas through the downstream flow path 24 to the low-pressure turbine 18, where the gas again rotates the turbine blades and transmits mechanical power to the fan, output shaft, etc. (not shown). It becomes a means to do so. low pressure turbine 1
The gas discharged from 8 then leaves the gas turbine engine 10 via an exhaust duct or nozzle (not shown).

A portion of the compressor discharge air that generally enters the region of the combustor 14 is circulated to cool the hot portions of the turbine engine 10. Some of the air surrounding the combustor 14 enters the combustor walls and cools the interior surfaces of the combustor through convection and/or film cooling processes. Another portion of this air is directed into the first stage turbine blades 26, thus providing cooling through impingement and diffusion processes. A further portion of the compressor discharge air is routed along the path indicated by the arrows in FIG.
Cool down 0.

It should be appreciated that during high power operating regimes, high temperature operating conditions prevail and a significant amount of cooling air is required to cool the hot portions of the turbine.
However, there are other modes of engine operation that require less cooling air. Furthermore, there are even certain modes of engine operation that do not require cooling air at all. It is an intent and object of the present invention to provide cooling air in a manner that addresses the need for cooling the engine and at the same time makes the use of cooling air economical whenever possible to increase engine efficiency. It is to modulate the flow.

FIG. 2 shows one embodiment of a cooling airflow modulator 30 of the present invention installed within a portion of a gas turbine engine. The illustrated device is incorporated into an engine that utilizes a centrifugal compressor, the outlet 32 of which is located radially outside of the combustor 14. A compressor provides high pressure compressor discharge air to a region 34 surrounding the combustor. As previously mentioned, a large portion of this compressor discharge air is directed to the combustor 14 to assist in the combustion process occurring within the combustor.

One or more inlet ports 36 to the modulator 30 are connected to the combustor 14 to prevent sand or dirt particles present in the compressor discharge air from directly entering the inlet ports 36 of the device. It is arranged radially outward and upstream of the outlet 32 of the compressor. Since the cooling air entering this system is used to cool the turbine blades, which have very small cooling air passages, it is very important to keep them free of dirt particles. If dirt enters the system, it will tend to block these cooling air passages, thereby interfering with the cooling process and potentially damaging the hot components of the turbine.

An inlet port 36 directs compressor discharge air into a corresponding duct 38 of the cooling system. It goes without saying that the engine can be provided with any number of inlet ports 36 and corresponding ducts 38, generally depending on the dimensions of the ducts and the design requirements of the engine. Each duct 38 channels compressor discharge air radially inwardly at a location upstream from the combustor 14 and then directed axially downstream within the engine generally toward the region of the high pressure turbine 16 .

Before entering the turbine section, cooling air is collected in a 360° circumferential manifold 40. This manifold serves as a source of high pressure cooling air to provide internal cooling of the turbine section. From this source, a flow of cooling air is directed through a tangential flow accelerator 42 towards a rotating turbine rotor 43 . Cooling air enters rotor cold plate chamber 46 through inlet hole 44 . Air is distributed radially outwardly from chamber 46 into the interior of turbine blade 20 . The airflow cools the turbine blades 20 and exits into the turbine flow path 24 through cooling holes in the turbine blades.

The accelerator 42 is connected to the cooling inlet hole 4 of the turbine rotor.
The acceleration of the tangential flow to a speed level approximately commensurate with the speed of 4 increases the static pressure in the cold plate chamber 46 relative to the turbine rotor, thus increasing the internal pressure of the turbine blades. Sufficient pressure levels are required within the vanes 20 to prevent the cooling flow from reversing and drawing hot exhaust gases into the interior of the vanes, referred to as backflow.

It will be appreciated that two circumferential manifolds 40 are shown in FIG. A predetermined number of multiple air ducts 38 supply air to a single manifold 40, and these predetermined air ducts are provided with valve means 48 immediately downstream of the inlet port 36. Valve means 48 are provided to modulate the airflow through these intended air ducts 38 to modulate the cooling airflow to one manifold 40 and therefore one accelerator 42. The advantages of this configuration will be explained later.

Any of a variety of types of valves may be used to construct valve means 48. Examples of possible devices are plug-type valves, bow-type valves or flapper valves as shown in FIG.

The illustrated flap valve consists of a pivoting flap 50 which rests on the wall of the duct 38 and can keep the duct open. To close the flap valve, extend the actuation arm 52 and
The flap is then pivoted into the position shown in phantom to close the air duct 38.

Extension and retraction of the actuation arm 52 is effected by an external actuation device 54. The actuating device may be mechanical, electrical, pneumatic, hydraulic, or any other type of actuating device. The type of actuating device used is not critical, but it is most convenient if the device 54 is located outside the skin 56 of the engine. The actuating device 54 can then be used, for example in order to service the actuating device.
becomes easier to access. Locating the actuator externally also prevents the actuator from being exposed to high temperatures within the combustor region 34 of the engine. It is relatively simple to extend the necessary control means to the actuator 54, whatever the control means, in order to operate the actuator correctly during different operating modes of the engine.

As previously mentioned, the embodiment of the cooling airflow modulator shown in FIG. 2 has two 360 DEG manifolds 40 mounted one above the other adjacent to each other. In the illustrated embodiment, each of the two manifolds is connected directly to one or more corresponding air ducts 38. With this configuration,
An inherent advantage is obtained that when a certain air duct 38 is closed by the valve means 48, the remaining air ducts remain open to the unmodulated manifold 40. open air duct 3
The unmodulated manifold connected to 8 is
It remains relatively unaffected by any pressure loss that may occur due to closing the valve.

By configuring the individual duct and manifold combinations in this way, a normal full pressure level is maintained for the open air duct and manifold combination, resulting in an unmodulated tangential flow across the accelerator. A full pressure ratio is obtained and flow acceleration is maximized, and the cooling air chamber 46 is
And the pressure within the turbine blade 20 becomes even higher.
As previously mentioned, higher pressures are required to maintain backflow margin in the vanes 20. This backflow allowance prevents hot gases from the turbine section from flowing into the blades 20 during operation of the turbine.

Modulating the flow for all manifold and accelerator combinations reduces the pressure ratio across the accelerator, the tangential velocity of the air leaving the accelerator, and finally the air pressure within the vanes 20.

Therefore, by using two accelerators 42, manifolds 40 and ducts 38 and modulating only one duct, manifold and accelerator combination,
The pressure ratio across the unmodulated accelerator is kept full and vane pressure losses are avoided. For this reason,
The cooling airflow can be reduced even more significantly while still maintaining sufficient backflow margin. manifold 40
It goes without saying that the total number of manifolds, as well as the number of manifolds corresponding to unmodulated accelerators 42, can be varied.

As shown, by choosing the location of the duct inlet upstream of the compressor outlet 32, the momentum of particles entrained in the combustor discharge air causes such particles to bypass the duct inlet 36. It will be understood that relatively clean cooling air can be taken in because it follows a trajectory like this. The proximity of the duct inlet 36 to the outer skin of the engine allows the actuator 54 and all moving parts to be mounted externally, thus improving reliability, simplicity and ease of maintenance. .

FIG. 3 shows another embodiment of the cooling air flow modulator 3.
0 is shown. Again, the engine utilizes a centrifugal compressor to deliver compressor discharge air to a region 34 surrounding the combustor 14.

Compressed discharge air enters air duct 38 via inlet port 36. Air flow in this inlet port 36 is controlled by a projecting plug valve 58. This valve can be actuated by any of a variety of types of actuating device 54.

Again, cooling air is directed radially inwardly by the air ducts 38 and then axially downstream generally towards the region of the turbine section. In the embodiment shown in FIG.
The air enters a 360° circumferential manifold 40 where it is collected before being pumped through a tangential accelerator 42 to a rotating turbine section.

Although this invention has been specifically described with reference to preferred embodiments and modified embodiments, the idea of this invention can easily be modified to other embodiments, and those skilled in the art will be able to do so within the scope of this invention. We can change the structure. For example, although the invention has been described in connection with directing a flow of cooling air to rotating high pressure turbine components, the invention may be used to cool other rotating or stationary sections of a gas turbine engine. Other modifications will be readily apparent to those skilled in the art. It is to be understood that such modifications are included within the scope of the invention as defined by the claims.

[Brief explanation of the drawing]

FIG. 1 is a simplified cross-sectional view of a portion of a gas turbine engine using a typical turbine cooling air system;
FIG. 3 is a simplified sectional view of a portion of a gas turbine engine using an embodiment of the present invention, and FIG. 3 is a simplified sectional view of a portion of a gas turbine engine using another embodiment of the invention. Explanation of main symbols, 12: Compressor, 14: Combustor, 16: High pressure turbine, 32: Outlet, 36: Inlet port, 38: Duct, 40: Manifold, 4
2: tangential flow accelerator, 48: valve means, 52: actuation arm, 54: actuation device.

Claims (1)

[Scope of Claims] 1. A centrifugal compressor, a combustor, and a turbine portion are disposed coaxially within a casing of an engine, and the compressor is disposed in front of the combustor,
A gas turbine engine in which the turbine section is disposed aft of the combustor, and the compressor acts to supply compressor discharge air for cooling the turbine section, the gas turbine engine providing cooling air to the turbine section. a modulating apparatus having an outlet of the compressor disposed radially outwardly relative to the combustor and facing rearward; and first and second ends, the first end being the outlet of the combustor. the second end is located radially inward of the combustor, and the first end further includes an inlet port located forward of the outlet of the compressor. a manifold in flow communication with a duct having a duct and the second end of the duct, the manifold collecting cooling air discharged from the duct as a source of cooling air for cooling the turbine section; a tangential flow accelerator disposed in flow communication and operative to direct said cooling air to said turbine section; and valving means operative to modulate the flow of cooling air within said duct. and the valve means includes an actuator disposed radially outwardly of the casing, an actuator arm extending from the actuator through the casing, and a valve means positioned within the duct for modulating airflow through the duct. and including a valve operatively connected to said actuation arm. 2. The apparatus of claim 1, wherein said valve comprises a plug valve positionable within said inlet port. 3. The device according to claim 1, wherein the valve is a positionable flap valve. 4. The apparatus of claim 1, wherein the turbine section has a plurality of turbine blades and a chamber operative to receive cooling air for distribution to the turbine blades, and the duct comprises first and second parallel flow ducts, the manifolds comprising first and second parallel flow circumferential manifolds, the tangential flow accelerator being in flow communication with the chamber of the turbine section; first and second parallel flow circumferential tangential flow accelerators arranged such that said valve means modulates only the airflow to said first duct, first manifold and first tangential flow accelerator; wherein the second duct, second manifold and second tangential flow accelerator act to provide an unrestricted flow path from the compressor to the turbine section.