Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
1999-09-23
2001-06-05
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C416S09600A
Reexamination Certificate
active
06241468
ABSTRACT:
THE FIELD OF THE INVENTION
The present invention relates generally to cooling arrangements for gas turbine components and in particular to improvements to the arrangement and configuration of cooling passages which are provided within the walls of a component and are arranged to provide film cooling of the component.
BACKGROUND OF THE INVENTION
Certain components, in particular in the combustor and turbines, of a gas turbine engine are subject, in operation, to high temperature gas flows. In some cases the high temperature gas flows are at temperatures above the melting point of the component material. In order to protect the components, and in particular the surface of the components adjacent to the high temperature gas flows, from these high temperatures, various cooling arrangements are provided.
Generally such arrangements utilise relatively cool compressed air, which is bled from the compressor section of the gas turbine engine, to cool and protect the components subject to the high operating temperatures.
A well known method of cooling and protecting gas turbine components from the high temperature gas flows is film cooling in which a film of cooling air is provided along the surface of the component exposed to the high temperature gas flows. The film of cooling air is produced by conducting a flow of cooling air through a plurality of passages which perforate the wall of the component. The air exiting the passages is directed, by the passages, to flow in a boundary layer along surface of the component. This cools the wall of the component exposed to the high temperature gas flow and provides a protective film of cool air between the high temperature gas flow and the component surface. The protective film assists in keeping the high temperature gas flow away from the surface of the component wall.
The arrangement and configuration of the passages are carefully designed to provide, and ensure, an adequate boundary layer flow of cooling air along the surface of the component. The passages are accordingly generally angled in the flow direction of the hot gas stream so that the cooling air flows in a downstream direction over the surface of the component.
Ideally it is desired that the boundary layer should flow over substantially the entire surface of the component downstream of the passages. However it has been found that the cooling air leaving the passage exit generally forms a cooling stripe no wider than, or hardly wider than, the dimension of the exit of the passage. Limitations on the number, size, and spacing of the passages results in gaps in the protective cooling layer provided and/or areas of reduced protection/cooling.
To overcome this it has been proposed, in for example U.S. Pat. No. 3,527,543, to use divergent passages where the cross section of the passages increases towards the passage exit at the surface of the component exposed to the hot gas flow. The cooling air which flows through the passages is thereby partially spread out over a larger area of the surface. Whilst this is an improvement over a constant cross section passage it has been found that the air exiting the passage generally still does not spread out enough to provide a continuous film of cooling air between the typical spacing of the passages.
A further development of the diverging passages is to arrange the passages sufficiently close to each other such that the outlets of the adjacent passages, on the surface of the component exposed to the hot gas flows, intersect laterally to define a common outlet in the form of a laterally extending slot. The cooling air expands as it passes though the passages and exits from this common slot as a substantially continuous film. Such an arrangement is described more fully in U.S. Pat. No. 4,676,719 which also references other similar arrangements which are described in U.S. Pat. No. 3,515,499 and Japanese Patent Number 55-114806.
In these prior art arrangements the passages are divergent and the cross sectional area of the passage increases towards the exit. This slows down, and diffuses, the flow of cooling air therethrough. As is taught in the prior art this slowing of the flow is important in assisting in spreading the flow of cooling air, in a boundary layer, along and over the surface of the component. Another important consideration in the design of such film cooling arrangements is to ensure that a stable boundary layer is provided over the surface of the component, and that this boundary layer remains attached to the surface of the component to thereby protect the surface from the high temperature gas stream. This boundary layer flow of cooling air is also required to withstand fluctuations and variations in the hot gas stream, that may occur during operation, to ensure that adequate cooling and protection is provided throughout the operation of the engine. In addition the flow through the passages and along the surface of the component should be as aerodynamically efficient as possible.
In an additional variation slots within the walls of the component can be used to direct the cooling air to the outer surface of the component. Such an arrangement is described in U.S. Pat. Nos. 2,149,510, 2,220,420 and 2,489,683.
Although such arrangements provide a good flow of cooling air along and over the surface of the component the structural strength of the walls of the component is reduced. This is also true, albeit to a lesser extent, with the arrangements where the passages intersect at their exits to form a common exit slot.
It is therefore desirable to provide an improved gas turbine engine component cooling arrangement and configuration, and in particular to provide an improved arrangement and configuration of cooling passages that address the above mentioned problems and/or offers improvements to such cooling arrangements generally.
SUMMARY OF THE INVENTION
According to the present invention there is provided a gas turbine engine component comprising a wall with a first surface which is adapted to be supplied with a flow of cooling air, and a second surface which is adapted to be exposed to a hot gas stream, the wall further has passage walls which define therein a plurality of passages, which interconnect passage inlets in said first surface of the component to passage outlets in said the second surface, the passages, passage walls defining the passages, cooling air and the hot gas stream arranged such that in operation a flow of cooling air is directed from the passage inlets to the passage outlets through said passages to provide a flow of cooling air over at least a portion of the second surface; wherein a cross sectional area of each of the passages in a direction of cooling air flow through a passage, progressively decreases overall from the passage inlets to the passage outlets such that in use the flow of cooling air from the passage inlets to the passage outlets through each passage is accelerated.
Preferably the passage outlet in said second surface comprises a slot defined by the passage in said second surface. The passage inlet in said first surface preferably has a different shape to the passage outlet slot.
The passage outlets of at least two of the plurality of passages may be combined to produce a common outlet.
Preferably at the passage outlet of at least two adjacent passages, at least part of the passage walls defining the adjacent passages substantially intersect the second surface of the wall exposed to the hot gas stream.
The cross section, substantially perpendicular to the direction of flow through the passage, of the passage inlet may be substantially circular or elliptical or rectangular
Preferably the passage walls, which define the passages through the walls of the component, are profiled such that in a first direction substantially perpendicular to a cooling flow direction through the passage they converge towards a centre line through the passage, and in a second direction also perpendicular to a flow direction through the passage they diverge from the centre line of the passage. Furthermore the first direction in
Lock Gary D
Oldfield Martin L G
Look Edward K.
Manelli Denison & Selter PLLC
McAleenan James M
Rolls-Royce plc
Taltavull W. Warren
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