JPH0423087B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to turbine engines, and more particularly to gas turbine engines having a turbine shroud assembly around the gas turbine.

[Conventional technology]

Gas turbine engines must maintain relatively small tolerances between the turbine blades and the surrounding engine in order to operate effectively. This is necessary to minimize power losses due to expanding gas passing between the ends of the turbine blades and the surrounding shroud. In turbine engines, expansion of the turbine impeller relative to the engine is a problem that must be addressed during design and during engine operation.

As mentioned above, the efficiency of a gas turbine engine is highly dependent on the tightness of the gas flow through the gas turbine. When the hot gas impinges on the turbine impeller and the extending turbine blades, there is significant expansion of the turbine impeller. Several steps may be taken to keep the turbine impeller and surrounding turbine shroud structure in close proximity. First, it is appropriate to try to ensure that the expansion ratio of the turbine shroud structure is essentially the same as or slightly greater than the expansion ratio of the turbine impeller. To achieve this,
It is necessary to design a turbine shroud structure to expand equally throughout its entire environment. This type of structure was published by Karl W. on February 17, 1981.
U.S. Patent No. 1 for "Expansion Control Ring for Turbine Shroud Assembly" granted to Karstensen
No. 4251185. The structure disclosed in the above-mentioned patent is capable of inflating a shroud assembly that is concentric with the engine axis, but it is possible to inflate the shroud assembly concentrically with the engine axis if the turbine impeller temporarily eccentrically expands during engine acceleration or deceleration. This requires a larger gap between the blades and the shroud. Accordingly, abradable shroud structures are also utilized in the aforementioned patents. Such shroud structures do not allow for various turbine blade contacts with the shroud structure without undue damage to the turbine blades. In particular, since the abradable portions of the shroud structure are made softer than the turbine blades, such contact causes wear of the shroud structure.

In other applications, turbine blade tips are designed such that a certain amount of the turbine blade tip wears. These types of turbine blades are commonly referred to as "squeal tips" because contact of the blades with the turbine shroud produces "squeal".
The only disadvantage of "squeal tip" blades is that the cooling passages normally found in gas turbine blades are easily blocked by turbine tip wear. If the cooling passages become blocked in the turbine blades, the turbine blades will overheat and then fail.

In both abradable shroud-type structures and "squeal tip"-type structures, the turbine impeller has sufficient clearance between the turbine impeller and the shroud structure to cause metal abrasion in either the shroud structure or the turbine tip. With each contact between the gas turbine and the shroud structure, there was not only increased clearance, but also the potential for abraded particles to damage the power turbine downstream of the gas turbine.

[Problem to be solved by the invention]

Since the above-mentioned known prior art has limitations, an object of the present invention is to provide a turbine engine that can rotate without contacting other members even though the turbine blades are eccentric, replacing the prior art. do.

[Means to solve the problem]

That is, the turbine engine according to the present invention includes a shroud assembly mounted concentrically around a turbine impeller, and the shroud assembly includes a pair of rings, a spacer ring disposed between the rings, and an expansion control ring, wherein the spacer ring has a plurality of notches formed on its inner periphery, and the expansion control ring has a plurality of extending ledges corresponding to the notches formed on its outer periphery. the ledge extends into the notch;
Each notch has a space on both sides of the corresponding ledge and in the radial direction, and when the turbine impeller is operated eccentrically or concentrically with respect to the engine axis, the expansion control ring The present invention is characterized in that the space maintains overall concentricity with the turbine impeller.

[Effect]

Therefore, the shroud structure is moved eccentrically relative to the axis of the engine via the floating expansion control ring;
This maintains concentricity with the turbine impeller.

〔Example〕

Referring to FIG. 1, portions of a turbine shroud assembly 10 are illustrated. A turbine shroud assembly, such as the shroud assembly 10 shown in FIG. (schematically illustrated in Figures 4A-4E) for use in gas turbine engines.

As shown in FIG.
consists of three main parts, a spacer ring 14, a pair of manifold rings 28 and 30, and an expansion control ring 20. Spacer ring 14 has a plurality of notches 16 formed therein to receive corresponding lobes 18 formed in outwardly extending web 32 of expansion control ring 20. The expansion control ring 20 has a plurality of shroud segments 2
It has 2. The shroud segment 22 and expansion control ring 20 provide a floating interface between the surrounding engine-fixed spacer ring 14 and the rotating turbine blades 12.

Referring now to FIG. 2, inflation control ring 20
It can be seen how the and associated shroud segments 22 are floatingly attached to the engine casing 24. The spacer ring 14 defines a plurality of holes 26 through which a plurality of corresponding bolts 27 can be passed. On each side of spacer ring 14 are manifold rings 28 and 30, respectively. The purpose of these manifold rings is more clearly described in US Pat. No. 4,251,185. It is noted that these rings, in addition to providing support for the shroud assembly, direct cooling air to the shroud assembly.

As can be seen in FIG. 2, bolts 27 are attached to manifold rings 28 and 30 and spacer rings
It is attached to the engine casing 24 through.

Spacer ring 14 has a dimension T ₁ that is slightly thicker than thickness T ₂ of web 32 of expansion control ring 20 . This greater thickness allows movement of expansion control ring 20 relative to manifold rings 28 and 30 and spacer ring 14.

Referring now to FIG. 3, inflation control ring 20
An enlarged view of the spacer ring 14 is shown. Expansion control ring 20 has an outer circumference 34 with radius R ₁ while spacer ring 14
has an inner circumference with radius R ₂ . Radius R ₂ is the radius
It is clear that R ₁ is greater than R 1 by a predetermined amount.
Similarly, in FIG.
has a width W ₁ , while each notch 16 has a width W 1
It can be seen that it has W ₂ . Furthermore, the depth of each notch is equal to a predetermined amount D, while the height of each ledge is equal to H.

The relationship between each notch and each ledge may then be defined as W ₂ -W ₁ /2<[(R ₂ +D)-(R ₁ +H)].

This clearance relationship controls the concentric movement of the expansion control ring.

Industrial Applicability With the parts assembled as described above, the expansion control ring 20 in a gas turbine engine can be moved eccentrically as described in the next paragraph.

Referring now to FIG. 4A, the expansion control ring is schematically illustrated as a circle at 20, while the spacer ring is also schematically illustrated as a circle at 14. A schematic turbine impeller 11 with associated turbine blades 12 is shown in a rest position in FIG. 4A. Prior art devices having abradable shroud segments, such as those described in the above-mentioned U.S. Pat. If there is no concentricity, the shape will be as shown in Figure 4B. In particular, it can be seen in FIG. 4B that the turbine impeller 11' has moved downwardly so that the associated turbine blade 12' contacts the expansion control ring 20'. Due to the abradable structure, the expansion control ring then loses its circular shape as shown in Figure 4C. This loss of circularity results in a loss of efficiency of the turbine engine due to increased clearance between the blades and the turbine impeller, as shown in FIG. 4C. The illustrations in Figures 4A-4E are exaggerated to better clarify the problem.

A "squeal tip" type vane, as described in the Background of the Invention, is shown in Figure 4D, with vanes 12'' decreasing in length around the entire turbine impeller.
The loss in efficiency is much greater than in the embodiment shown in Figure 4C. In Figure 4D, the "squeal tip"
The vanes 12'' have been worn to concentrically increase the gap between the vanes 12'' and the expansion control ring 20''.
Of course, the spacer ring 14'' and the turbine impeller 11'' remain unaffected.

The invention is schematically illustrated in FIG. 4E, where the turbine impeller 11 has a spacer ring 14
eccentric to the housing as shown by. As a result of the eccentricity of turbine impeller 11, initial contact occurs between vanes 12 and shroud segments 22, as best shown in FIG. This involves movement of the expansion control ring 20 from a concentric position to an eccentric position with respect to the engine axis 40, but maintains the concentricity of the turbine impeller 11. As the turbine impeller returns to concentric relationship with the turbine axis 40, the expansion control ring 20 may move or float relative to the turbine impeller. For this reason, business trip 1
8 and notches 20 provide a means for the expansion control ring 20 to maintain general concentricity with the turbine impeller 11 even when the turbine impeller 11 operates eccentrically with respect to the engine axis 40.

Referring now to FIGS. 1 and 3, the expansion control ring 20 is able to move circumferentially due to the gap between the ledge 18 and the side of the notch 16, which gap causes the expansion control ring 20 and the spacer ring to move in the circumferential direction. It is possible to eliminate damage to the internal parts of the engine due to the difference in expansion ratio between the engine and the engine. The side clearance between the ledge 18 and the notch 16 is smaller than the radial clearance between the notch 16 and the ledge 18 to limit circumferential movement of the expansion control ring, thereby preventing unnecessary movement between the two parts. This is very important.

The invention described above is particularly advantageous in overcoming the need to use either a "squeal tip" or an abradable shroud as described in the Background of the Invention. In the past, abradable shrouds have been subject to oxidation or corrosion due to high gas temperatures and, after a short time, erosion due to high gas velocities. Thus, in addition to the possibility of permanent eccentricity as shown in FIG. 4C above, the actual clearance between the turbine impeller and expansion control ring 20 increases due to this erosion and corrosion problem. . If "squeal tips" are used on all blades of the turbine impeller, there is increased clearance between the shroud structure and all the blades, as shown in FIG. 4D. Furthermore, when there are cooling passages provided in the turbine blades 12, wear around the edges of the "squeal tips" can block airflow through the turbine blades and have a detrimental effect on the cooling of the engine itself.

〔Effect of the invention〕

As is clear from the above description, according to the configuration of the present invention, the spacer ring has a plurality of notches formed on its inner periphery, and each notch defines a space on both sides and in the radial direction of the corresponding bulge of the expansion control ring. Therefore, damage to the inside of the turbine engine due to a difference in expansion ratio between the expansion control ring and the spacer ring can be prevented, and the expansion control ring can maintain overall concentricity with the turbine impeller.

[Brief explanation of drawings]

1 is a section of a turbine shroud assembly within a turbine engine forming an embodiment of the invention; FIG. 2 is a cross-section of a turbine shroud assembly with associated attachment elements forming an embodiment of the invention in conjunction with a turbine blade; FIG. Figure 3 is a detailed view of portions of the expansion control ring and spacer ring forming an embodiment of the invention;
and FIGS. 4A-4E are a series of schematic illustrations of turbine impellers and associated shroud structures of this embodiment and the prior art. 10... shroud assembly, 11... turbine impeller, 14... spacer ring, 16... notch, 18... ledge, 20... expansion control ring,
28, 30...a pair of manifold rings, 40...
...Engine axis line.

Claims (1)

[Claims] 1. A turbine engine comprising a shroud assembly mounted concentrically around a turbine impeller, the shroud assembly having a pair of rings, a spacer ring disposed between the rings, and an expansion control ring. The spacer ring has a plurality of notches formed on its inner periphery, the expansion control ring has a plurality of extending ledges formed on its outer periphery corresponding to the notches, and the ledges are formed in the notches. each notch has a space on either side of the corresponding ledge and radially outwardly when the turbine impeller is operated eccentrically or concentrically with respect to the engine axis. , wherein the expansion control ring maintains overall concentricity with the turbine impeller by the space.