Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-06-17
2001-05-29
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
Reexamination Certificate
active
06238183
ABSTRACT:
This invention relates to improvements to gas turbine engine airfoils.
In particular, the invention concerns improvements to an internal air cooling system for a gas turbine engine airfoil and especially a nozzle guide vane by providing means to reduce the effect of blockages in certain critical passages in the cooling system, more particularly narrow cooling holes in an impingement and film cooling system, due to trapped particulate material entrained in the cooling air.
In an impingement cooling system it is typical for the cooling air having passed through several passages to enter a plenum from which at least a proportion exits via a number of narrow diameter holes to provide impingement cooling jets onto another part of wall. In the event one of these holes becomes blocked, for example by air borne particles trapped in the hole itself, the associated cooling jet is lost to the detriment of overall cooling efficiency. Deterioration is progressive until eventually the airfoil suffers damage due to the overheating.
In the case where the impingement cooling jets subsequently feed airfoil film cooling systems, blockage of the impingement holes will reduce film cooling flows. Furthermore, any particles which pass through the impingement plate holes may subsequently block the film cooling holes leading to severe overheating and rapid deterioration of the airfoil leading edge.
It is accordingly an objective of the present invention in its most general form to provide a means for trapping particulate material entrained in a fluid.
It is a further objective of the present invention to provide a means for reducing blockage of cooling holes in an airfoil or guide vane of a gas turbine engine.
According to one aspect of the present invention there is provided a gas turbine engine airfoil having an internal air system including air delivery impingement holes
48
having a certain predetermined width, wherein, in use, the air system may carry particles of sufficiently large size to block the air delivery impingement holes
48
, the airfoil including a partition member through which the internal air passes via at least one hole comprising an impingement hole exit aperture
52
of said predetermined width in the downstream surface of the partition member, and a non-circular impingement hole entry aperture
54
formed in the upstream surface of the partition member which has a minor dimension less than or equal to the impingement hole exit aperture
52
width whereby to exclude particles of greater size and a substantially larger major dimension such that the passage of air into the hole is largely unaffected by particles which become trapped in the impingement hole entry aperture
54
.
According to another aspect of the invention each air delivery impingement hole is supplied through an individual non-circular impingement hole entry aperture
54
having said major and minor dimensions.
According to a further aspect of the invention each air delivery impingement hole
48
is supplied from the base of a passageway or channel formed in the upstream side of the partition member and the minor dimension constituting the width of the channel is less than the width of the air delivery impingement hole
48
.
According to a still further aspect of the present invention there is provided a means for reducing blockage of film cooling apertures
48
in a guide vane of a gas turbine engine by particulate material entrained in high-pressure cooling air directed within the vane, the vane being a hollow body externally of airfoil form, there being provided a partition within the vane for dividing the hollow region into first and second regions, the first region being adapted to receive high pressure cooling air, the second region being adapted to be at a pressure lower than that of the first region, the partition being provided with a plurality of apertures providing flow communication between the first and second regions and arranged to direct cooling air towards the inside of the guide vane, wherein the partition is provided with a channel on the high pressure side, said plurality of apertures being located in the base of the channel, the inlet area of the channel being greater than the total cross-section area of the apertures, and the width of the channel distal to its base being less than or equal to the minimum diameter of any one of said apertures, whereby an entrained particle that is larger than the diameter of the apertures is trapped by the channel.
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Emery Martin A J
Self Kevin P
Williamson Robert P E
Look Edward K.
McAleenan James M
Oliff & Berridg,e PLC
Rolls-Royce plc
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