This application is the US National Stage of International Application No. PCT/EP2007/058434, filed Aug. 15, 2007 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 06017536.1 DE filed Aug. 23, 2006, both of the applications are incorporated by reference herein in their entirety.
The invention relates to a turbine engine rotor disc and the stress reduction in the at least one cooling passage extending there-through in an essentially radial direction with respect to the axis of rotation of the rotor disc.
Gas turbine engines typically include several rotor discs which carry a plurality of rotor blades extending radially outwardly into the hot working medium gases which makes it usually necessary to provide cooling to the blades. To remove heat from the rotor blades, cooling air is tapped from the engine's compressor and directed into passages within the disc and blade interiors. The cross-section of the passages is typically circular, since this is the cheapest and easiest to produce. During operation, rotational forces induce tangential stress in the disc material where the openings of the cooling air passages are subject to major hoop stresses with a high risk of crack initiation.
EP 0 814 233 B1 describes a gas turbine engine rotor disc with radially extending cooling air supply passages, each passage having a cross-sectional configuration which renders the ends of passages less likely to act as site of hoop-stress induced cracks.
U.S. Pat. No. 4,344,738 describes a gas turbine engine rotor disc with cooling air holes where the elongated axis of each cooling air hole lies in a plane perpendicular to the axis of symmetry of the disc to reduce tangential stress concentration factors.
U.S. Pat. No. 4,522,562 describes the cooling of turbine rotors where the disc is equipped with two sets of channels bored respectively close to each of the sides of the disc and in conformity with its profile in which the cooling air of the turbine blades flows in order to cool the disc.
An object of the invention is to provide an improved gas turbine rotor disc, especially a new cooling passage geometry for a gas turbine engine rotor disc leading to a longer disc lifetime due to a greater resistance to crack initiation at the outer openings of rotor disc cooling passages.
This object is achieved by the claims. The dependent claims describe advantageous developments and modifications of the invention.
An inventive rotor disc with cooling passages comprises a plurality of passages having an essentially radial orientation relative to an axis of rotation of the rotor disc with a slight downstream inclination relative to the flow of hot gases in the turbine, each passage having an inlet opening and an outlet opening. When rotating at very high speed, the disc generates high levels of hoop stress especially in the disc rim acting in circumferential direction of the disc. These stresses could result in the formation of cracks in the outlet openings of the cooling passages in the disc rim. This crack formation is favoured by acute edges in the outlet opening especially when the profile runs along a circumferential direction of the disc. A cut-out is arranged at the passage at an outlet opening end of the passage to remove the sharp-edged portion of the outlet opening. The profile of the cut-out is contoured for example as a compound radius and has a first central radius and a second peripheral radius, where the first radius is larger than the second radius and both radii are merging tangentially to achieve a smooth transition.
Such a design of the rotor disc with cooling passage is an optimum compromise in terms of stress concentrations induced by hoop stresses in the disc rim and radial stresses in the disc post. As a result, the peak stress is reduced thus enhancing the fatigue life of the component.
The invention will now be further described with reference to the accompanying drawings in which:
In the drawings like references identify like or equivalent parts.
In order to enhance the resistivity of the upstream part of the outlet 4 the acute-edged portion is cut out in a radial direction relative to the rotation axis of the rotor disc 1. The upstream profile of the cut-out 8 is contoured as a compound radius having a first central radius 12 and a second peripheral radius 13, the first radius 12 being larger than the second radius 13. The ratio of the first and the second radius falls into the range 2:1 to 20:1.
The difference between the prior art and the present invention is illustrated with regard to
With reference to
In an alternative arrangement the compound radius may be defined by more than two different radii.
In another alternative arrangement the compound radius may also be defined by a polynomial or a combination of one or more radii and a polynomial.
Number | Date | Country | Kind |
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06017536 | Aug 2006 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/058434 | 8/15/2007 | WO | 00 | 2/19/2009 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2008/022954 | 2/28/2008 | WO | A |
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Number | Date | Country |
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0 814 233 | Dec 1997 | EP |
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Number | Date | Country | |
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20100014958 A1 | Jan 2010 | US |