Patent Description:
As known, a gas turbine assembly for power plants comprises a compressor assembly, a combustor assembly and a turbine assembly. The compressor assembly is configured for compressing incoming air supplied at a compressor inlet. The compressed air leaving the compressor assembly flows into a closed volume (called "plenum") and from there into the combustor assembly. This combustor assembly comprises usually a plurality of burners configured for injecting fuel (at least one type of fuel) into the compressed air flow. The mixture of fuel and compressed air enters a combustion chamber where this mixture ignites. The resulting hot gas flow leaves the combustion chamber and flows by the turbine assembly performing a rotating work on a rotor connected to a generator. Usually the same rotor supports also the compressor assembly and it defines the main axis of the system. As known, the turbine assembly comprises a plurality of stages, or rows, of rotating blades that are interposed by a plurality of stages, or rows, of stator vanes. The rotating blades are supported by the rotor whereas the stator vanes are supported by a casing (called "vane carrier") that is concentric and surrounding the turbine assembly.

In order to achieve a high efficiency, the hot gas flow has to have a very high turbine inlet temperature. However, in general this high temperature involves an undesired high NOx emission level. In order to reduce this emission and to increase operational flexibility without decreasing the efficiency, a so called "sequential" gas turbine is particularly suitable. In general, a sequential gas turbine performs two combustion stages in series. Today at least two different kinds of sequential gas turbines are known. According to a first embodiment, the gas turbine comprises a first combustor and the second combustor that are annular shaped and are physically separated by a turbine, called high pressure turbine. Downstream the second combustor a second turbine unit is present (called low pressure turbine).

According to a second embodiment of a sequential gas turbine, the gas turbine is not provided with the high-pressure turbine and the combustor assembly is realized in form of a plurality of can-combustors wherein each can-combustor comprises a first combustor and a second combustor arranged directly one downstream the other inside a common casing can-shaped. These two examples of gas turbine assemblies have been cited only as non-limiting examples wherein the stator ring of the present invention can be applied.

In the following specification, the terms "circumferential, radial, axial, outer and inner" will refer to the rotor or turbine axis (that is parallel to the main air/hot gas flow). The terms "downstream and upstream" will refer to the main direction of the air/hot gas flow. As foregoing reported, and as known, the turbine assembly comprises a plurality of stages, or rows, of stator vanes wherein in each row is defined by a plurality of vanes arranged adjacent to each other along the circumferential direction. Each vane comprises a body substantially radially shaped extending between an outer end supported by the outer casing and an inner free end facing (and in proximity to) the rotor. In this configuration, each vane (in particular the corresponding free end) may vibrate or oscillate during the use of the system. In order to reduce or limit these undue movements, it is known to provide each vane row with a so called "stator ring" that is an assembly ring-shaped configured for connecting to each other the free ends of a vane row. <CIT>, that can be considered as the closest prior art document for the present invention, discloses an example of a stator ring formed by a plurality of ring segments circumferentially coupled to each other. Due to the vane vibration and the different thermal expansions between the vane and the corresponding stator ring segment, the coupling between the vane and the ring segment may wear out and consequently this coupling may become not stable. In order to avoid this problem, the solution disclosed in <CIT> is to provide the ring segment with a plurality of so called "pressure bolts". Each pressure bolt is a pushing device configured for being housed in a ring segment and for acting against the vane by means of a restoring force generated by a compressed spring supported by the bolt itself. In this way the vibrations of the vane and the different thermal expansions between vane and corresponding ring segment are dumped avoiding coupling instability.

Starting from the above, the scope of the present invention is to improve the disclosure of <CIT>, i.e. to provide an improved stator ring segment comprising a plurality of the pressure bolts or damping pins.

Prior art documents <CIT> and <CIT> disclose ring segments configured for being coupled to the free ends of the turbine vanes by radial damping coupling devices.

Accordingly, a primary scope of the present invention is to provide a new and inventive ring segment device for turbine vanes, i.e. a device configured for being coupled to one or more free ends of vanes and for realizing, cooperating with adjacent segments, a stator ring structure around the axis of the turbine in proximity of the rotor. In general, the starting point of the present invention is to provide a ring segment device comprising:.

In this known configuration, according to the main aspect of the invention the ring segment device moreover comprises:.

Advantageously, in this way the pushing force generated by the damping pin devices against the turbine vanes is not locally concentrated (as in <CIT>) but distributed along the bar. Thus, any local wear of the vane platform at the damping pin devices is avoided and the coupling stability improved.

In each ring segment device the bar and the ring segment have substantially the same circumferential extent so that for each segment a single bar is present acting to one or more vanes.

For each vane is provided a damping pin device and each hole housing the corresponding damping pin device has an axis configured so that, in use, each damping pin device is axially arranged in order to better damp the axial vibrations of the free ends of the vanes.

Preferably, each hole housing the corresponding damping pin device is a passing hole comprising a first end obtained in an upstream face of the ring segment and a second end housing a portion of the bar. Consequently, each damping pin device comprises a cylindrical base configured for being coupled (preferably by a screwing coupling) to the first end of the corresponding hole and a head acting in a sprung manner against the bar.

Each damping pin device moreover comprises:.

The sliding coupling between the piston and the head is performed, for instance, by a pin fixed to head protruding inside a slotted hole obtained in the piston.

Preferably, a safety lock device is provided for each damping pin device configured for acting against the base of the corresponding damping pin device. For instance, the safety lock device may comprise a pin housed in an inclined hole obtained in the upstream face of the ring segment and acting against a V shaped circumferential slot obtained in the base of the damping pin device.

Even if the first coupling (i.e. before the activation of the damping pins) between the ring segment and the vane platforms is guarantee by corresponding hook portions obtained in these elements, preferably a mounting device is provided configured for coupling the ring segment to a turbine vane before the activation of the damping pin devices. This mounting device may comprise a radial pin housed in a hole obtained in the inner face of the ring segment and having a protruding free end configured for entering a seat obtaining in the turbine vane. This mounting device moreover comprises a screw for fixing in position the radial pin that is accessible by the upstream face of the segment (as the inclined safety lock device and the axial damping pin devices).

As foregoing cited, the ring segment device of the present invention can be preferably used in a gas turbine assembly for power plant. In general, a gas turbine assembly is an assembly having an axis and comprising:.

In general, a plurality of ring segment devices of the present invention may be used for forming a stator ring connecting the free ends of a row or stage of turbine vanes.

The combustor sector may comprise a plurality of can combustors, wherein each can combustor houses in series a first and a second burner. Alternatively, the gas turbine assembly may comprise in series a first burner, a high pressure turbine, a second burner and a low pressure turbine.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. Other advantages and features of the invention will be apparent from the following description, drawings and claims.

The features of the invention believed to be novel are set forth with particularity in the appended claims.

The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which:.

In cooperation with the attached drawings, the technical contents and detailed description of the present invention are described thereinafter according to preferred embodiments, being not used to limit its executing scope. Any equivalent variation and modification made according to appended claims is all covered by the claims claimed by the present invention.

Reference will now be made to the drawing figures to describe the present invention in detail.

Reference is now made to <FIG> that is a schematic view of a gas turbine assembly wherein the reference M refers to the main air/hot gas flow directions. As known, this gas turbine assembly <NUM> for power plants comprises a compressor assembly <NUM>, a combustor assembly <NUM> and a turbine assembly <NUM>. The compressor assembly is configured for compressing incoming air supplied at a compressor inlet. The compressed air leaving the compressor assembly <NUM> flows into the combustor assembly <NUM>. This combustor assembly <NUM> comprises usually a plurality of burners configured for injecting fuel (at least one type of fuel) into the compressed air flow. The mixture of fuel and compressed air enters a combustion chamber where this mixture ignites. The resulting hot gas flow leaves the combustor assembly <NUM> and enters the turbine assembly <NUM> performing a rotating work on a rotor <NUM> having an axis A and connected to a generator <NUM>.

<FIG> discloses a first non-limiting detailed example of a gas turbine assembly for power plant <NUM> that can be provided with a plurality of new ring segment devices according to the present invention. According to the embodiment of <FIG> this gas turbine is a so called "sequential-combustion gas turbine" provided with a high-pressure and a low-pressure turbine. Following the main gas flow <NUM>, the gas turbine <NUM> of <FIG> comprises a compressor <NUM>, a first combustor <NUM>, a high-pressure turbine <NUM>, a second combustor <NUM> and a low-pressure turbine <NUM>. The compressor <NUM> and the two turbines <NUM>, <NUM> are integral of or are connected to a common rotor <NUM> rotating about an axis <NUM> and surrounded by a concentric casing <NUM>. The compressor <NUM> is supplied with air and has rotating blades <NUM> and stator vanes <NUM> configured to compress the air entering the compressor <NUM>. Exiting the compressor, the compressed air flows into a plenum <NUM> and from there into a plurality of first burners <NUM> of the first combustor <NUM> arranged in a circular pattern around the axis <NUM>. Each first burner <NUM> is configured for injecting at least one type of fuel (connected to at least one first fuel supply <NUM>) into the compressed airflow. Preferably, this first burner <NUM> may be defined as a "premix" burner because is configured for mixing the compressed air and the injected fuel before the ignition. The fuel/compressed air mixture flows into a first combustion chamber <NUM> annularly shaped, where this mixture ignites. During start-up this mixture is initially ignited by an ignitor, for instance by a spark igniter; once ignited the ignition is self-sustaining and the ignitor is turned off. The resulting hot gas leaves the first combustor chamber <NUM> and is partially expanded in the high-pressure turbine <NUM> performing work on the rotor <NUM>. Downstream of the high-pressure turbine <NUM> the partially-expanded hot gas flows into a row of second burners <NUM> where at least one type of fuel is injected by fuel lances <NUM> (each burner has one lance). The partially-expanded gas has a high temperature and contains sufficient oxygen for further combustion that occurs by self-ignition in the second combustion chamber <NUM> arranged downstream of the row second burners <NUM>. These second burners <NUM> are also called "reheat" burners. The reheated hot gas leaves the second combustion chamber <NUM> and flows in the low-pressure turbine <NUM> where it is expanded performing work on the rotor <NUM>. The low-pressure turbine <NUM> comprises numerous stages: rows of rotor blades <NUM> arranged in series in the main flow direction. Such rows of blades <NUM> are interposed by rows of stator vanes <NUM>. The rotor blades <NUM> are connected to the rotor <NUM> whereas the stator vanes <NUM> are connected to a vane carrier <NUM> that is a concentric casing surrounding the low-pressure turbine <NUM>.

Reference is now made to <FIG> that is a schematic view of a second not-limiting example of a gas turbine that can be provided with a plurality of ring segment device according to the present invention. Also this gas turbine <NUM> is a "sequential-combustion gas turbine" that can be provided with the innovative features according to the present invention. In particular, <FIG> discloses a partial view of a gas turbine <NUM> with a compressor <NUM>, a turbine <NUM> and a sequential combustor <NUM>. The sequential combustor <NUM> of <FIG> comprises a plurality of so-called can combustors, i.e. a plurality bolt-on can structures wherein each can combustor is provided with first burners <NUM>, a first combustion chamber <NUM>, second burners <NUM> and a second combustion chamber <NUM>. Upstream of the second burner <NUM> an mixer may be provided for adding air into the hot gas leaving the first combustion chamber <NUM> and creating turbulence in the air/hot gas mixture. When the hot gas leaves the second combustion chamber <NUM> it then expands in the turbine <NUM> performing work on a rotor <NUM>.

The more detailed examples of turbine assemblies disclosed in <FIG> have been described only as non-limiting examples of turbomachine that can be provided with a plurality of ring segment devices of the present invention. Indeed the present invention can be applied in general in every kind of turbine assembly where at least a row or stage of vane is present. In view of this generalization <FIG> discloses a front view (i.e. a view along the hot gas flow direction) of a plurality of ring segment devices of the present invention forming a stator ring connecting the free ends of a row or stage of vanes. In this figure the reference A' refers to the axial direction (i.e. parallel to the axis A of the rotor), the reference R the radial direction and the reference C the circumferential direction. Thus, <FIG> discloses a stator ring <NUM> formed by a plurality of ring segment devices <NUM> adjacent to each other along the circumferential direction C connecting as a single ring the free inner ends of a row of vanes. The reference <NUM> refer to the row in general and the reference <NUM> to each single vane.

<FIG> is an enlarged view of a portion of <FIG> disclosing a portion of a single ring segment device <NUM> according to the present invention. As disclosed, the single ring segment device <NUM> comprises a ring segment <NUM> as main body provided with an outer face <NUM> configured, i.e. shaped, for being coupled to the inner face of one or more vane platforms <NUM>. The shape of each platform <NUM> and the corresponding shape of the outer face <NUM> of the ring segment <NUM> may vary; in this example the coupling is performed by hook portions of the vanes (upstream oriented) housed in corresponding seats obtained in the ring segment <NUM>. This ring segment <NUM> moreover comprises an upstream face <NUM> (substantially radial) and an inner face <NUM> (substantially axial) facing the rotor. Each ring segment <NUM> comprises a lateral lip <NUM> configured to be housed in a corresponding lateral seat of the adjacent ring segment <NUM> for forming a single circumferential ring. The reference <NUM> refer to a second body of the ring segment device <NUM> of the present invention, i.e. a circumferential bar that act as an intermediate body between the ring segment <NUM> and the platform <NUM>. In this example, the bar <NUM> is single bar having a circumferential extent substantially equal to the corresponding segment <NUM> and it is downstream arranged, i.e. it acts against the downstream hook <NUM> of the platform <NUM>. References <NUM> and <NUM> reported in <FIG> refer to components of the ring device <NUM> that will be described in detail in the following figures, namely damping pins <NUM>, locking devices <NUM> and mounting device.

In particular, <FIG> disclose a damping pin <NUM> isolated from the segment <NUM>. As known, the scope of this damping pin is to improve the coupling between vane/s and ring segment by damping coupling vibrations and different thermal deformations. According to this example, the damping pin device <NUM> has an axis A" (in use parallel to the axial direction A) and it is configured for being housed in a corresponding axial hole <NUM> obtained in the upstream face <NUM>. Consequently, each damping pin device <NUM> comprises a cylindrical base <NUM> configured for being coupled (preferably by a screwing coupling) to the first end <NUM> of the corresponding hole <NUM>.

Each damping pin device <NUM> moreover comprises:.

In this configuration, by screwing the base <NUM> in the first end <NUM> of the corresponding hole <NUM> the piston <NUM> is moved toward the bar <NUM> and the spring device <NUM> is progressively compressed toward the head <NUM> (fixed against the bar) increasing the pushing force.

The sliding coupling between the piston <NUM> and the head <NUM> is performed, for instance, by a pin <NUM> integral with respect to head <NUM> and protruding inside a slotted hole obtained in the piston <NUM>. The reference <NUM> in <FIG> refer to holes configured for housing the ends of a fork tool for screwing the damping pin <NUM> in the corresponding hole <NUM>.

<FIG> disclose two different configurations of the damping pin <NUM> in a ring segment device <NUM>. In particular <FIG> discloses a first step of the activation procedure wherein the base <NUM> is only in part screwed in the first end <NUM> of the hole <NUM> and, therefore, the spring device <NUM> is not fully compressed. <FIG> discloses the configuration of the segment ring device <NUM> when the base <NUM> is fully screwed in the first end <NUM> of the hole <NUM> and the spring <NUM> is thus compressed for generating via the head <NUM> the required sprung force against the bar <NUM>.

<FIG> disclose two additional devices of the ring segment device <NUM> of the present invention. In particular, <FIG> discloses a safety lock device that is provided for locking in position a corresponding damping pin device <NUM>. In the disclosed example of <FIG>, the safety lock device comprises a pin <NUM> housed in an inclined hole <NUM> obtained in the ring segment <NUM> and acting against a V shaped circumferential slot <NUM> of the base <NUM> of the damping pin device <NUM>. <FIG> discloses a mounting device configured for coupling the ring segment <NUM> to a turbine vane platform <NUM> before the activation of the damping pin devices <NUM>. According to this example, the mounting device comprises a radial pin <NUM> housed in a radial hole <NUM> of the ring segment <NUM> and having a protruding free <NUM> configured for enter a seat <NUM> obtaining in a turbine vane platform <NUM>. The mounting device moreover comprising an axial screw <NUM> for fixing in position the radial pin <NUM>.

Claim 1:
A ring segment device for turbine vanes of a power plant turbine assembly having an axis (A), preferably a gas turbine assembly; the ring segment device (<NUM>) comprising:
- a ring segment (<NUM>) having a first face (<NUM>) configured for being coupled to a free end (<NUM>) of at least two adjacent turbine vanes (<NUM>);
- at least a damping pin device (<NUM>) housed in a corresponding hole (<NUM>) obtained in the ring segment (<NUM>); the damping pin device (<NUM>) being configured for coupling the ring segment (<NUM>) to the corresponding turbine vane/s (<NUM>) in a sprung manner; characterized in that
the ring segment device (<NUM>) moreover comprises:
- a circumferential bar (<NUM>) having substantially the same circumferential extent of the ring segment (<NUM>) arranged between the damping pin device (<NUM>) and the turbine vane/s (<NUM>) so that the force generated by the damping pin device (<NUM>) against the turbine vane/s (<NUM>) is not locally concentrated but distributed along the bar (<NUM>);
wherein each hole (<NUM>) has an axis configured so that, during the use of the ring segment device (<NUM>), the damping pin device (<NUM>) is axially arranged with respect to the axis (A) of the power plant turbine assembly.