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Publication Date: 2014-Sep-03
Document File: 4 page(s) / 48K

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The invention proposes a technique that provides positive retention mechanism for patch ring for rabbet repair in gas turbine. The technique includes a tapered patch ring. The patch ring is designed such that fits on rotor centering feature (rabbet) and a taper feature helps the ring remain in its location during operation also. The technique enables self-retention capability of low radius rabbet patch ring for both male and female rabbet configurations.

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The present invention relates generally to a gas turbine and more particularly to a technique for repairing gas turbine rotor wheel rabbet.

In general, gas turbine compressor rotors have independent wheels mounted with blades and buckets. The wheels are aligned and centered together using a centering feature, referred to as rabbets. Rotor discs are assembled together using the rabbet features by means of positive interference. During operational conditions rotor disc experiences high rotational speed and axial growth due to high thermal gradients which results in wear out of the rabbet. Consequently, the rabbets loose its interference fit. Due to interference loss, rabbets slide axially on top of each other which results in damage to rabbets surface. The damage is found to be of significant order which requires a check. Similar kind of scenario is observed in rotors in gas turbine which are operated for longer duration of time and when the wheels are disassembled. Conventionally, rabbet surface is restored by providing coating or installing a patch ring which helps rotor to achieve the interference fit. However, such a repair mechanism using patch ring is not applied to stage 1 through 7 as there is no positive retention mechanism available.

A conventional technique includes a method of assembling a rotary machine having a casing extending at least partially around a rotor. The method includes providing a diaphragm patch ring.

Another conventional technique includes a centering feature to bearing assembly of a turbomachine to provide optimum operating characteristics of a squeeze film damper. A compact compliant centering support is provided for the squeeze film damper that interfaces between a bearing outer race, and an outer support structure. The compact compliant centering support damper includes a ring with bumpers spaced around the circumference at the inside and outside diameters to form spring elements between the bumpers.

One other conventional technique includes a compressor case, and an associated method, repaired from damage to a segment of a stator ring hook. A patch plug is slid into the space from one flange face. Shape of the patch plug is complementary to a shape of the missing material space and inter-fitting therein, with an end of the patch plug located at the one flange face to face an opposed half of the case with the two halves together.

Another conventional technique includes a casing patch assembly which includes a patch seal having two ring-type seals with different performance characteristics.

However, the above mentioned conventional techniques do not provide any significant rotor centering feature solution.

Therefore there is a need in the art to provide a technique that provides retention mechanism for patch ring for rotor centering feature repair in the gas turbine.



Figure 1 depicts rotor assembly with p...