Cooling air supply system

BACKGROUND OF THE INVENTION

0001The present invention relates to gas turbine engines and more particularly to an improved system for reducing leakage of fluid and for providing fluid at a desired pressure to a point of use

0002Air is bled from the high pressure compressor and used to cool various engine components including a blade outer air seal assembly in the high pressure turbine section of the engine. In the past, there has been substantial pressure losses in this cooling air due to leakage. As a result of these losses, it has been difficult to maintain the required cooling levels and the desired back flow margin at the blade outer air seal assembly.

0003<patcit id="pcit0001" dnum="GB1317992A"><text>GB-A-1317992</text></patcit> discloses a cooling arrangement for cooling a turbine casing.

SUMMARY OF THE INVENTION

0004Accordingly, it is an object of the present invention to provide an improved system for delivering cooling air to a blade outer air seal assembly.

0005It is a further object of the present invention to provide an improved system as above which reduces pressure losses due to leakage.

0006The foregoing objects are attained by the system of the present invention.

0007In accordance with the present invention, a system for optimizing cooling air supply pressure is provided as claimed in claim 1.

0008Other details of the ejector for cooling air supply pressure optimization, as well as other advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

0009<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is an illustration of a portion of a gas turbine engine containing the system for optimizing cooling air supply pressure of the present invention; and</li><li><figref idref="f0001">FIG. 2</figref> is an enlarged view of the system for optimizing cooling air supply pressure in accordance with the present invention.</li></ul>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

0010Referring now to <figref idref="f0001">FIG. 1</figref>, a gas turbine engine 10 has a combustor 12 and a fluid passageway 14 for conducting air bled from a high pressure compressor (not shown). The bleed air is used to supply cooling air to a blade outer air seal assembly 16. In the past, it has been difficult to supply the cooling air to the seal assembly 16 at a desired pressure. This is due to a leakage which occurs at a location 18 between the chamber 34 forming a high pressure fluid source and a plenum 19 which provides cooling air to the seal assembly 16.

0011In accordance with the present invention, a system 30 for optimizing the pressure of the cooling air supplied to the blade outer air seal assembly 16 is provided. The system 30 includes an inlet 32 for allowing high pressure bleed air from the high pressure compressor flowing through the passageway 14 to enter the chamber 34 which acts as the high pressure fluid source. The pressure within the chamber 34 approximately equals of the pressure at the exit of the high pressure compressor. Opposite the inlet is a nozzle 36 which is sized to create a desired flow of cooling air exiting the chamber 34 at a desired rate. The nozzle 36 is positioned within a diaphragm 37 which forms at least one wall of the chamber 34.

0012As can be seen from <figref idref="f0001">FIG. 2</figref>, an ejector 38 is aligned with the outlet 40 of the nozzle 36. A cavity 42 surrounds the outlet 40 of the nozzle 36 and the inlet 44 of the ejector 38. The pressure of the cooling air within the cavity 42 is approximately 75% of the pressure in plenum 19 and equivalent to the pressure at location 18. By reducing the pressure in cavity 42 to that at location 18, leakage at location 18 is eliminated. In order to deliver cooling air at an appropriate pressure, to the plenum 19 and the blade outer air seal 46, air is supplied to the inlet 44 of the ejector 38 by the nozzle 36. Since the static pressure at the inlet 44 is lower than the pressure in the cavity 42, air within the cavity 42 is drawn into the ejector 38. This reduces the leakage of air through the location 18 between the supply source chamber 34 and the plenum 19. The pressure of the cooling air being delivered to the blade outer air seal 46 is increased to the desired level by sizing the ejector 38 to increase the pressure of the air being delivered to the plenum 19.

0013The cooling air which is delivered to the blade outer air seal 46, via the plenum 19, flows through a series of impingement holes 48 onto an outer surface 50 of the seal 46 and then discharges through cooling holes 55 in seal 46. It is important to deliver the cooling air at the correct pressure so as to maintain the back flow margin (the difference in the pressure on the inner and outer surfaces 54 and 50 respectively of the seal 46) so that the cooling air flows through the holes 55 in seal 46.

0014The system of the present invention optimizes the pressure drop, cooling air supply pressure, and down stream leakage between the cooling air supply chamber 34 and the pressurized plenum 19, which delivers the cooling air to the blade outer air seal 46. The result is maintaining the required cooling airflow and back flow margin at the blade outer air seal 46 while reducing the leakage to below the level of a system that does not include the ejector 38.

0015While only one nozzle 34 and one ejector 38 have been illustrated, the system actually has a number of nozzles 34 and a number of aligned ejectors 38 around the circumference of the engine.

0016It is apparent that there has been provided in accordance with the present invention an ejector for cooling air supply pressure optimization 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 alternatives, modifications and variations will become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variation as fall within the broad scope of the appended claims.