Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
2000-05-30
2001-11-20
Kwon, John (Department: 3747)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
C416S09700R
Reexamination Certificate
active
06318963
ABSTRACT:
The invention relates to improvements in a gas turbine airfoil internal air system.
In particular it concerns improvements for screening particulates over a predetermined size carried in the air system and discharging said oversize particulates.
There is a need to cool certain components such as nozzle guide vanes in gas turbine engines by providing a flow of relatively cool air to the interior of the airfoil section. Simply making the airfoil sections hollow and flowing air therethrough is inefficient at cooling and wasteful of air. It is preferable to concentrate cooling air in certain regions of the airfoil and one way of doing this is by way of directing concentrated jets of cooling air at certain parts of the internal surface, in a technique known as impingement cooling. The airfoil is made, usually cast, as a hollow section with internal locating features which position an insert, comprising a perforate panel or sheet, a short distance away from the internal surface. When the internal cavities are connected to a source of pressurised cooling air small holes in the panel cause jets of cooling air to impinge on the interior walls of the airfoil. In addition, small holes may be provided through the airfoil walls to allow some of the spent cooling air to diffuse therethrough and establish an air film over the external surface.
A drawback of internal air systems of this kind is susceptibility of the small holes to blockage by large particulates which may be carried in the cooling air flow. This drawback is especially evident when the gas turbine engine is operated in environments where large air borne particulates, eg dust and sand particles, are present. The particulates accumulate in the air system progressively causing blockages which disrupt the cooling air supply. When these blockages become significant affected parts of the cooled component overheat and rapidly begin to suffer heat related damage. Component failure can occur quite quickly. Our co-pending application GB 9813251.7 (Agents Ref BL 2637 UK) and subsequent applications claiming priority therefrom, provides a solution to these problems by seeking to exclude particulates above a certain size from parts of the air system with holes and passages small enough to be susceptible to blocking by those particulates, and ensuring that even where particles become trapped etc supply of cooling air is not prematurely inhibited. These arrangements ensure that a supply of cooling air is maintained at a predetermined level for a much longer period of time than has been achieved previously. However, in order to avoid a build-up of screened particulates causing further blockages it is necessary to discharge them from the air system.
The present invention seeks to provide a solution to this further problem and may be used alone or in conjunction with the above mentioned previous arrangements to effect the complete removal and discharge of oversize particulates from the internal air system.
Therefore, according to one aspect of the present invention there is provided a gas turbine airfoil having an internal air system comprises means for screening solid particulates over a predetermined size, a plenum where said oversize particulates may be isolated and discharge means leading from said plenum into an external airflow to discharge the oversize particles.
REFERENCES:
patent: 4257734 (1981-03-01), Guy et al.
patent: 5779438 (1998-07-01), Wilfert
patent: 6238182 (2001-05-01), Meyer
patent: 0 965 728 A2 (1999-12-01), None
Emery Martin A J
Self Kevin P
Kwon John
Oliff & Berridg,e PLC
Rolls-Royce plc
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